feat(dictation): reason model — speaking tooltip on a disabled mic + shared error resolver (#309)

The dictation mic could be grey/disabled while silently showing "Start
dictation", and Mantine's native `disabled` set pointer-events:none so the
Tooltip never fired at all — the UI knew the cause but told the user nothing.
Runtime error strings were also duplicated verbatim across the two dictation
hooks.

- New dictation-status.ts: the single source of truth. A DictationUnavailableReason
  enum (connecting/offline/read-only/unsupported/busy) + a DictationErrorCode enum,
  pure classifiers (classifyGetUserMediaError / classifyTranscriptionError) and
  resolvers (resolveUnavailableLabel / dictationErrorMessage). All user-facing
  dictation strings are formed here; the verbatim server message still wins for
  transcription errors.
- page-editor publishes dictationAvailabilityAtom { isEditable, reason } computed
  at the source (editable/edit-mode/showStatic/collab status): connecting vs
  offline (stuck) vs read-only. DictationGroup forwards the reason to MicButton.
- MicButton is reason-aware: a disabled mic shows the cause-specific tooltip. The
  disabled-hover silence is fixed by marking disabled the Mantine way
  (data-disabled/aria-disabled + click guard) instead of the native attribute, so
  the Tooltip fires — applied to both the idle (reason) and error (errorMessage)
  states.
- Both hooks route every error through the shared resolver (deleting the
  duplicated transcriptionErrorMessage), and expose errorMessage for the tooltip.
  Wording is byte-identical to each hook's original (incl. the batch hook's
  DOMException name prefix and the verbatim server message).
- i18n: 3 new reason keys in en-US + ru-RU, and the previously-missing ru-RU
  dictation error translations.

Tests: dictation-status.test.ts (all classifier/resolver branches, incl. server
message passthrough) + mic-button.test.tsx (disabled mic shows the reason text,
uses data-disabled not native disabled — fails against the pre-fix code).
vitest: 5 files / 32 passed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/src/features/editor/atoms/editor-atoms.ts

@@ -1,6 +1,7 @@
 import { atom } from "jotai";
 import { Editor } from "@tiptap/core";
 import { PageEditMode } from "@/features/user/types/user.types.ts";
+import type { DictationUnavailableReason } from "@/features/dictation/dictation-status";
 
 export const pageEditorAtom = atom<Editor | null>(null);
 
@@ -15,3 +16,15 @@ export const showLinkMenuAtom = atom(false);
 // Current page's edit mode — initialized from the user's saved preference on
 // first load, can be toggled locally without persisting to the server.
 export const currentPageEditModeAtom = atom<PageEditMode>(PageEditMode.Edit);
+
+// Whether the dictation mic can start, and (when it can't) the cause-specific
+// reason the mic button surfaces as a tooltip. Published by the page editor,
+// consumed by DictationGroup -> MicButton.
+export type DictationAvailability = {
+  isEditable: boolean;
+  reason: DictationUnavailableReason | null;
+};
+export const dictationAvailabilityAtom = atom<DictationAvailability>({
+  isEditable: false,
+  reason: null,
+});