Token auto-discovery, tx history, balance polling, EIP-6963, UI overhaul

Major changes:
- Fetch token balances and tx history from Blockscout API (configurable)
- Remove manual token discovery (discoverTokens) in favor of Blockscout
- HD address gap scanning on mnemonic import
- Duplicate mnemonic detection on wallet add
- EIP-6963 multi-wallet discovery + selectedAddress updates in inpage
- Two-tier balance refresh: 10s while popup open, 60s background
- Fix $0.00 flash before prices load (return null when no prices)
- No-layout-shift: min-height on total value element
- Aligned balance columns (42ch address width, consistent USD column)
- All errors use flash messages instead of off-screen error divs
- Settings gear in global title bar, add-wallet moved to settings pane
- Settings wells with light grey background, configurable Blockscout URL
- Consistent "< Back" buttons top-left on all views
- Address titles (Address 1.1, 1.2, etc.) on main and detail views
- Send view shows current balance of selected asset
- Clickable affordance policy added to README
- Shortened mnemonic backup warning
- Fix broken background script constant imports

src/content/index.js

@@ -1,15 +1,17 @@
 // AutistMask content script — bridges between inpage (window.ethereum)
 // and the background service worker via extension messaging.
 
-// Inject the inpage script into the page's JS context
-const script = document.createElement("script");
-script.src = (typeof browser !== "undefined" ? browser : chrome).runtime.getURL(
-    "src/content/inpage.js",
-);
-script.onload = function () {
-    this.remove();
-};
-(document.head || document.documentElement).appendChild(script);
+// In Chrome (MV3), inpage.js runs as a MAIN-world content script declared
+// in the manifest, so no injection is needed here.  In Firefox (MV2), the
+// "world" key is not supported, so we inject via a <script> tag.
+if (typeof browser !== "undefined") {
+    const script = document.createElement("script");
+    script.src = browser.runtime.getURL("src/content/inpage.js");
+    script.onload = function () {
+        this.remove();
+    };
+    (document.head || document.documentElement).appendChild(script);
+}
 
 // Relay requests from the page to the background script
 window.addEventListener("message", (event) => {

src/content/inpage.js

@@ -1,9 +1,7 @@
 // AutistMask inpage script — injected into the page's JS context.
-// Creates window.ethereum (EIP-1193 provider).
+// Creates window.ethereum (EIP-1193 provider) and announces via EIP-6963.
 
 (function () {
-    if (typeof window.ethereum !== "undefined") return;
-
     const CHAIN_ID = "0x1"; // Ethereum mainnet
 
     const listeners = {};
@@ -45,7 +43,7 @@
         }
     }
 
-    function request(args) {
+    function sendRequest(args) {
         return new Promise((resolve, reject) => {
             const id = nextId++;
             pending[id] = { resolve, reject };
@@ -63,8 +61,21 @@
         networkVersion: "1",
         selectedAddress: null,
 
-        request(args) {
-            return request({ method: args.method, params: args.params || [] });
+        async request(args) {
+            const result = await sendRequest({
+                method: args.method,
+                params: args.params || [],
+            });
+            if (
+                args.method === "eth_requestAccounts" ||
+                args.method === "eth_accounts"
+            ) {
+                provider.selectedAddress =
+                    Array.isArray(result) && result.length > 0
+                        ? result[0]
+                        : null;
+            }
+            return result;
         },
 
         // Legacy methods (still used by some dApps)
@@ -119,10 +130,46 @@
             }
             return this;
         },
+
+        // Some dApps (wagmi) check this to confirm MetaMask-like behavior
+        _metamask: {
+            isUnlocked() {
+                return Promise.resolve(true);
+            },
+        },
     };
 
-    window.ethereum = provider;
-
-    // Announce via EIP-6963 (multi-wallet discovery)
+    // Set window.ethereum if no other wallet has claimed it
+    if (typeof window.ethereum === "undefined") {
+        window.ethereum = provider;
+    }
     window.dispatchEvent(new Event("ethereum#initialized"));
+
+    // EIP-6963: Multi Injected Provider Discovery
+    const ICON_SVG =
+        "data:image/svg+xml," +
+        encodeURIComponent(
+            '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32">' +
+                '<rect width="32" height="32" rx="6" fill="#000"/>' +
+                '<text x="16" y="23" text-anchor="middle" font-family="monospace" font-size="20" font-weight="bold" fill="#fff">A</text>' +
+                "</svg>",
+        );
+
+    const providerInfo = {
+        uuid: "f3c5b2a1-8d4e-4f6a-9c7b-1e2d3a4b5c6d",
+        name: "AutistMask",
+        icon: ICON_SVG,
+        rdns: "berlin.sneak.autistmask",
+    };
+
+    function announceProvider() {
+        window.dispatchEvent(
+            new CustomEvent("eip6963:announceProvider", {
+                detail: Object.freeze({ info: providerInfo, provider }),
+            }),
+        );
+    }
+
+    window.addEventListener("eip6963:requestProvider", announceProvider);
+    announceProvider();
 })();