fix(a11y): P3 — drop focus:outline-none on inputs; restore global :focus-visible

Phase 10a a11y audit (2026-04-29) flagged seven inputs across the app
that strip the global 2px :focus-visible outline (defined in app.css:251)
without providing a comparable replacement. Net effect: keyboard users
see at most a 1px border-colour shift on focus, sometimes nothing.

The fix removes the focus:outline-none override so the global rule
applies. Affected inputs:

- FilesPage: file-transcript textarea (F2).
- TasksPage: search input, quick-add input, inline list-edit, new-list
  input (T1, T2, T3, plus the new-list rename input).
- HistoryPage: top search, inline title rename, tag-add (H1).
- ImplementationRulesEditor: trigger/surface/task selects + speak-line
  input (S7).
- TaskSidebar, WipTaskList: quick-add inputs (S8).

The 1px focus:border-accent on inputs that had it is retained as a
secondary cue; the global 2px ring is now the primary indicator and
matches button focus across the app.

Resolves: F2, T1, T2, T3, H1, S7, S8.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/pages/FilesPage.svelte

@@ -241,7 +241,7 @@
     <Card classes="h-full flex flex-col">
       <textarea
         class="font-transcript flex-1 w-full bg-transparent text-text p-6
-               resize-none focus:outline-none placeholder:text-text-tertiary"
+               resize-none placeholder:text-text-tertiary"
         placeholder="Transcribed text will appear here..."
         bind:value={fileTranscript}
         data-no-transition