fix: standardize error display to use showError/hideError helpers

Replace inconsistent error display patterns across views:

- addWallet.js: replace showFlash() with showError('add-wallet-error', ...)
- importKey.js: replace showFlash() with showError('import-key-error', ...)
- addressDetail.js: replace direct DOM manipulation of export-privkey-flash
  with showError/hideError('export-privkey-error', ...)
- deleteWallet.js: replace direct DOM manipulation of delete-wallet-flash
  with showError/hideError('delete-wallet-error', ...)
- index.html: add dedicated error divs with min-h-[1.25rem] for add-wallet,
  import-key views; rename flash divs to error divs for export-privkey and
  delete-wallet views with consistent styling

All password/validation errors now use the showError()/hideError() helper
pattern with min-h-[1.25rem] error divs to prevent layout shift.
Status/success messages (scanning, wallet deleted) remain as showFlash().

Closes #87

src/popup/index.html

@@ -104,6 +104,10 @@
                         class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
                     />
                 </div>
+                <div
+                    id="add-wallet-error"
+                    class="text-xs mb-2 min-h-[1.25rem] hidden"
+                ></div>
                 <button
                     id="btn-add-wallet-confirm"
                     class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
@@ -162,6 +166,10 @@
                         class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
                     />
                 </div>
+                <div
+                    id="import-key-error"
+                    class="text-xs mb-2 min-h-[1.25rem] hidden"
+                ></div>
                 <button
                     id="btn-import-key-confirm"
                     class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
@@ -365,8 +373,8 @@
                     transfer all funds from this address. Never share it.
                 </p>
                 <div
-                    id="export-privkey-flash"
-                    class="text-xs mb-2 hidden"
+                    id="export-privkey-error"
+                    class="text-xs mb-2 min-h-[1.25rem] hidden"
                 ></div>
                 <div id="export-privkey-password-section" class="mb-2">
                     <label class="block mb-1">Password</label>
@@ -915,8 +923,8 @@
                     funds will be unrecoverable without your recovery phrase.
                 </p>
                 <div
-                    id="delete-wallet-flash"
-                    class="text-xs text-red-500 mb-2 hidden"
+                    id="delete-wallet-error"
+                    class="text-xs mb-2 min-h-[1.25rem] hidden"
                 ></div>
                 <div class="mb-2">
                     <label class="block mb-1">Password</label>

src/popup/views/addWallet.js

@@ -1,4 +1,4 @@
-const { $, showView, showFlash } = require("./helpers");
+const { $, showView, showFlash, showError, hideError } = require("./helpers");
 const {
     generateMnemonic,
     hdWalletFromMnemonic,
@@ -13,6 +13,7 @@ function show() {
     $("add-wallet-password").value = "";
     $("add-wallet-password-confirm").value = "";
     $("add-wallet-phrase-warning").classList.add("hidden");
+    hideError("add-wallet-error");
     showView("add-wallet");
 }
 
@@ -25,14 +26,16 @@ function init(ctx) {
     $("btn-add-wallet-confirm").addEventListener("click", async () => {
         const mnemonic = $("wallet-mnemonic").value.trim();
         if (!mnemonic) {
-            showFlash(
+            showError(
+                "add-wallet-error",
                 "Enter a recovery phrase or press the die to generate one.",
             );
             return;
         }
         const words = mnemonic.split(/\s+/);
         if (words.length !== 12 && words.length !== 24) {
-            showFlash(
+            showError(
+                "add-wallet-error",
                 "Recovery phrase must be 12 or 24 words. You entered " +
                     words.length +
                     ".",
@@ -40,21 +43,27 @@ function init(ctx) {
             return;
         }
         if (!isValidMnemonic(mnemonic)) {
-            showFlash("Invalid recovery phrase. Check for typos.");
+            showError(
+                "add-wallet-error",
+                "Invalid recovery phrase. Check for typos.",
+            );
             return;
         }
         const pw = $("add-wallet-password").value;
         const pw2 = $("add-wallet-password-confirm").value;
         if (!pw) {
-            showFlash("Please choose a password.");
+            showError("add-wallet-error", "Please choose a password.");
             return;
         }
         if (pw.length < 12) {
-            showFlash("Password must be at least 12 characters.");
+            showError(
+                "add-wallet-error",
+                "Password must be at least 12 characters.",
+            );
             return;
         }
         if (pw !== pw2) {
-            showFlash("Passwords do not match.");
+            showError("add-wallet-error", "Passwords do not match.");
             return;
         }
         const { xpub, firstAddress } = hdWalletFromMnemonic(mnemonic);
@@ -66,13 +75,15 @@ function init(ctx) {
                     firstAddress.toLowerCase(),
         );
         if (duplicate) {
-            showFlash(
+            showError(
+                "add-wallet-error",
                 "This recovery phrase is already added (" +
                     duplicate.name +
                     ").",
             );
             return;
         }
+        hideError("add-wallet-error");
         const encrypted = await encryptWithPassword(mnemonic, pw);
         const walletNum = state.wallets.length + 1;
         const wallet = {

src/popup/views/addressDetail.js

@@ -2,6 +2,8 @@ const {
     $,
     showView,
     showFlash,
+    showError,
+    hideError,
     balanceLinesForAddress,
     addressDotHtml,
     addressTitle,
@@ -310,8 +312,7 @@ function init(_ctx) {
         $("export-privkey-address").textContent = addr.address;
         $("export-privkey-address").dataset.full = addr.address;
         $("export-privkey-password").value = "";
-        $("export-privkey-flash").classList.add("hidden");
-        $("export-privkey-flash").textContent = "";
+        hideError("export-privkey-error");
         $("export-privkey-password-section").classList.remove("hidden");
         $("export-privkey-result").classList.add("hidden");
         $("export-privkey-value").textContent = "";
@@ -321,8 +322,7 @@ function init(_ctx) {
     $("btn-export-privkey-confirm").addEventListener("click", async () => {
         const password = $("export-privkey-password").value;
         if (!password) {
-            $("export-privkey-flash").textContent = "Password is required.";
-            $("export-privkey-flash").classList.remove("hidden");
+            showError("export-privkey-error", "Password is required.");
             return;
         }
         const btn = $("btn-export-privkey-confirm");
@@ -343,10 +343,9 @@ function init(_ctx) {
             $("export-privkey-password-section").classList.add("hidden");
             $("export-privkey-value").textContent = privateKey;
             $("export-privkey-result").classList.remove("hidden");
-            $("export-privkey-flash").classList.add("hidden");
+            hideError("export-privkey-error");
         } catch {
-            $("export-privkey-flash").textContent = "Wrong password.";
-            $("export-privkey-flash").classList.remove("hidden");
+            showError("export-privkey-error", "Wrong password.");
         } finally {
             btn.disabled = false;
             btn.classList.remove("text-muted");

src/popup/views/deleteWallet.js

@@ -1,4 +1,4 @@
-const { $, showView, showFlash } = require("./helpers");
+const { $, showView, showFlash, showError, hideError } = require("./helpers");
 const { state, saveState } = require("../../shared/state");
 const { decryptWithPassword } = require("../../shared/vault");
 
@@ -11,8 +11,7 @@ function show(walletIdx) {
     $("delete-wallet-name").textContent =
         wallet.name || "Wallet " + (walletIdx + 1);
     $("delete-wallet-password").value = "";
-    $("delete-wallet-flash").textContent = "";
-    $("delete-wallet-flash").classList.add("hidden");
+    hideError("delete-wallet-error");
     showView("delete-wallet-confirm");
 }
 
@@ -27,16 +26,15 @@ function init(_ctx) {
     $("btn-delete-wallet-confirm").addEventListener("click", async () => {
         const pw = $("delete-wallet-password").value;
         if (!pw) {
-            $("delete-wallet-flash").textContent =
-                "Please enter your password.";
-            $("delete-wallet-flash").classList.remove("hidden");
+            showError("delete-wallet-error", "Please enter your password.");
             return;
         }
 
         if (deleteWalletIndex === null) {
-            $("delete-wallet-flash").textContent =
-                "No wallet selected for deletion.";
-            $("delete-wallet-flash").classList.remove("hidden");
+            showError(
+                "delete-wallet-error",
+                "No wallet selected for deletion.",
+            );
             return;
         }
 
@@ -51,8 +49,7 @@ function init(_ctx) {
         try {
             await decryptWithPassword(wallet.encryptedSecret, pw);
         } catch (_e) {
-            $("delete-wallet-flash").textContent = "Wrong password.";
-            $("delete-wallet-flash").classList.remove("hidden");
+            showError("delete-wallet-error", "Wrong password.");
             btn.disabled = false;
             btn.classList.remove("text-muted");
             return;

src/popup/views/importKey.js

@@ -1,4 +1,4 @@
-const { $, showView, showFlash } = require("./helpers");
+const { $, showView, showError, hideError } = require("./helpers");
 const { addressFromPrivateKey } = require("../../shared/wallet");
 const { encryptWithPassword } = require("../../shared/vault");
 const { state, saveState } = require("../../shared/state");
@@ -7,6 +7,7 @@ function show() {
     $("import-private-key").value = "";
     $("import-key-password").value = "";
     $("import-key-password-confirm").value = "";
+    hideError("import-key-error");
     showView("import-key");
 }
 
@@ -14,30 +15,34 @@ function init(ctx) {
     $("btn-import-key-confirm").addEventListener("click", async () => {
         const key = $("import-private-key").value.trim();
         if (!key) {
-            showFlash("Please enter your private key.");
+            showError("import-key-error", "Please enter your private key.");
             return;
         }
         let addr;
         try {
             addr = addressFromPrivateKey(key);
         } catch (e) {
-            showFlash("Invalid private key.");
+            showError("import-key-error", "Invalid private key.");
             return;
         }
         const pw = $("import-key-password").value;
         const pw2 = $("import-key-password-confirm").value;
         if (!pw) {
-            showFlash("Please choose a password.");
+            showError("import-key-error", "Please choose a password.");
             return;
         }
         if (pw.length < 12) {
-            showFlash("Password must be at least 12 characters.");
+            showError(
+                "import-key-error",
+                "Password must be at least 12 characters.",
+            );
             return;
         }
         if (pw !== pw2) {
-            showFlash("Passwords do not match.");
+            showError("import-key-error", "Passwords do not match.");
             return;
         }
+        hideError("import-key-error");
         const encrypted = await encryptWithPassword(key, pw);
         const walletNum = state.wallets.length + 1;
         state.wallets.push({