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.

tests/test_email_library_bulk_actions.py

@@ -1,5 +1,5 @@
 from pathlib import Path
-from tests.helpers.js_modules import email_library_source
+from tests.helpers.js_modules import email_library_source, js_function_source
 
 
 _REPO = Path(__file__).resolve().parents[1]
@@ -9,20 +9,11 @@ _EMAIL_FIXTURE_HELPER = _REPO / "scripts" / "ody_eval_email_fixture.py"
 
 
 def _bulk_action_source() -> str:
-    text = email_library_source()
-    start = text.index("async function _bulkAction(action)")
-    end = text.index("\n}\n\n// _extractName", start) + 3
-    return text[start:end]
+    return js_function_source("_bulkAction")
 
 
 def _function_source(name: str) -> str:
-    text = email_library_source()
-    start = text.index(f"function {name}")
-    next_function = text.find("\nfunction ", start + 1)
-    next_async = text.find("\nasync function ", start + 1)
-    candidates = [idx for idx in (next_function, next_async) if idx != -1]
-    end = min(candidates) if candidates else len(text)
-    return text[start:end]
+    return js_function_source(name)
 
 
 def test_email_bulk_read_unread_calls_provider_write_routes():