refactor(email): split the email library into seven modules

`emailLibrary/index.js` goes from 11,375 lines to 6,187. What came out:

- `settingsPage.js` (879) — the Email Settings view, its form and controls,
  away/auto-reply including the calendar-event sync, and the display
  preferences. The inline-image preference lives here rather than with the
  renderer because the settings form owns writing it.
- `unsubscribe.js` (1,224) — the bulk-unsubscribe review flow. One exported
  entry point, its own localStorage keys, its own agent-tool-output listeners.
- `reader.js` (676) — opening an email as a docked tab or a floating window,
  plus the AI summary panel both of them share.
- `menus.js` (855) — the reader More menu, the card kebab menu, the bulk
  Actions menu and `_bulkAction`.
- `bodyRender.js` (871) — plain and threaded body rendering, inline MIME
  images, quote folding.
- `attachments.js` (491) — attachment chips and the deferred load for messages
  whose attachment list was not in the list response.
- `aiReply.js` (449) — AI-reply entry points, the per-message context draft,
  the translate and remind submenus.

The extracted modules import back from `index.js`, so the graph has cycles.
That is safe for hoisted function declarations and unsafe for a value read
during evaluation, so nothing crosses a module boundary except functions:
`API_BASE` is re-declared per module, the way `emailInbox.js` and
`emailShared.js` already do it, and `_autoReplyRefreshSeq` moves into
`state.js` because the settings page and the unread-badge refresh both write
it and an imported binding is read-only. The module-graph test enters the
package at each module in turn, which is the order that would expose a
dead-zone read.

Two test helpers grew while doing this. `js_function_source` replaces three
marker-pair slices ("from this signature down to that comment") whose end
marker had moved into another module — the slice ran past the function and
kept passing against the wrong text. Its first implementation balanced braces
by walking characters and ended `_toggleCardPreview` 18 lines early, because
the apostrophe in `// that's a scroll, not a nav` opened a string that ate the
braces after it. It now keys on the invariant the file actually holds: a
top-level declaration starts at column 0, so its closing brace is the next
lone `}` at column 0.

static/js/MODULE_SUMMARY.md

@@ -137,7 +137,7 @@ The largest and most central subsystem. Chat submission → backend SSE → prog
 | Module | Responsibility |
 |---|---|
 | **`gallery.js`** / **`galleryEditor.js`** | Gallery/image library and canvas editor entry points. |
-| **`emailInbox.js`** / **`emailLibrary.js`** | Email inbox reader and library modal. Sub-modules handle signatures, reply recipients, state, and signature folding. |
+| **`emailInbox.js`** / **`emailLibrary/`** | Email inbox reader and library modal. `emailLibrary.js` is a re-export wrapper; `emailLibrary/index.js` owns the panel, list and cards, with `settingsPage.js`, `unsubscribe.js`, `reader.js`, `menus.js`, `bodyRender.js`, `attachments.js` and `aiReply.js` alongside it plus the `utils.js` / `signatureFold.js` / `replyRecipients.js` / `state.js` leaves. |
 | **`calendar.js`** / **`calendar/utils.js`** / **`calendar/reminders.js`** | Calendar views, event forms, reminders. |
 | **`tasks.js`** | Scheduled task/recurring LLM job UI. |
 | **`notes.js`** | Notes and todo panel, reminders, pinboard. |