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/components/WipTaskList.svelte

@@ -53,7 +53,7 @@
       onkeydown={handleKeydown}
       placeholder="Add a task…"
       class="flex-1 px-3 py-2 rounded-lg bg-bg-input border border-border-subtle text-text text-[13px]
-        placeholder:text-text-tertiary focus:border-accent focus:outline-none"
+        placeholder:text-text-tertiary focus:border-accent"
       data-no-transition
     />
   </div>