fix: sign and export with each address's own derivation index (closes #510)

Sending, site transactions, site signatures and private key export
derived the key at the address's position in the wallet's list. After
an import whose scan passed over an unused index, or after removing an
address that was not the last, that position named another address's
key.

Each HD and xprv address record now stores the index it was derived at
(at wallet creation, by the import scan, by "+"), and
getSignerForAddress() derives at that index and refuses any key whose
address differs from the record's. The export screen reports that
refusal instead of calling the password wrong.

Model: opus-5-5

TODO.md

@@ -2,9 +2,10 @@
 
 - `git pull` `next` and cut a branch from it — one branch per issue, named
   `issue-<N>-<slug>`. Never branch from `main`.
-- Do the work as one commit whose title ends with ` (closes #N)`.
-- Add no entry to Completed Steps. What landed is recorded on the tracker and in
-  `git log`, where each commit title names the issue it closes.
+- Do the work as one commit whose title ends with ` (closes #N)`, with the
+  `TODO.md` update in that same commit.
+- Move Next Step to the top of Completed Steps; move the top item of Future
+  Steps into Next Step.
 - Run `make fmt`, then `make check`. A feature branch may be red; `next` and
   `main` may not.
 - Rebase onto current `next` immediately before pushing — other branches land on

src/popup/index.html

@@ -7,10 +7,9 @@
         <link rel="stylesheet" href="styles.css" />
     </head>
     <!-- Chrome gives extension pages a stylesheet of its own that sets the
-         font and its size on body, and a Tailwind class beats it only when
-         marked important: hence font-mono! and text-sm! rather than
-         font-mono and text-sm. -->
-    <body class="bg-bg text-fg font-mono! text-sm!">
+         font on body, and a Tailwind class beats it only when marked
+         important: hence font-mono! rather than font-mono. -->
+    <body class="bg-bg text-fg font-mono! text-sm">
         <div id="app" class="p-2 pr-5 overflow-x-hidden">
             <!-- ============ GLOBAL TITLE BAR ============ -->
             <div
@@ -88,14 +87,11 @@
 
                 <!-- Mnemonic form section -->
                 <div id="add-wallet-section-mnemonic">
-                    <!-- The die button shares the instruction's row: on a row
-                         of its own it pushes Import below the fold at
-                         360x600. -->
-                    <div class="mb-2 flex justify-between items-start gap-2">
-                        <p>
-                            Enter your 12 or 24 word recovery phrase below, or
-                            click the button to roll the die for a new one.
-                        </p>
+                    <p class="mb-2">
+                        Enter your 12 or 24 word recovery phrase below, or click
+                        the button to roll the die for a new one.
+                    </p>
+                    <div class="mb-1 flex justify-end">
                         <button
                             id="btn-generate-phrase"
                             class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer text-xs"

tests/e2e/firefox/run.js

@@ -128,18 +128,6 @@ step("the popup is drawn in the monospace font it declares", async (env) => {
     );
 });
 
-// The same check as the Chrome suite's (#456), so both browsers are held to
-// the same size.
-step("the popup's text is drawn at the 14px text-sm declares", async (env) => {
-    const size = await env.driver.execute(
-        "return getComputedStyle(document.body).fontSize;",
-    );
-    assert(
-        size === "14px",
-        "the popup's text is drawn at " + size + ", not at the 14px of text-sm",
-    );
-});
-
 // The recovery screen (#361): the Chrome suite's four cases, run before any
 // wallet exists for the same reason. With no wallet nothing saves on a timer,
 // so no save can write a good record over the unreadable one. The last of them

tests/e2e/run.js

@@ -113,18 +113,6 @@ test("the popup is drawn in the monospace font it declares (#418)", async (env)
     );
 });
 
-// The same stylesheet sets the size on body to 75%, which would draw the
-// popup at 12px.
-test("the popup's text is drawn at the 14px text-sm declares (#456)", async (env) => {
-    const size = await env.page.evaluate(
-        () => getComputedStyle(document.body).fontSize,
-    );
-    assert(
-        size === "14px",
-        "the popup's text is drawn at " + size + ", not at the 14px of text-sm",
-    );
-});
-
 // The empirical half of #182. The manifest change is only a claim about
 // what the CSP permits; this is the observation. Two things have to hold
 // together, and the run covers both: the popup realm compiles WASM (here),