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/components/fixed-toolbar/groups/dictation-group.tsx

@@ -1,7 +1,8 @@
 import { FC, useRef } from "react";
-import { Editor, useEditorState } from "@tiptap/react";
+import { Editor } from "@tiptap/react";
 import { useAtomValue } from "jotai";
 import { workspaceAtom } from "@/features/user/atoms/current-user-atom.ts";
+import { dictationAvailabilityAtom } from "@/features/editor/atoms/editor-atoms.ts";
 import { MicButton } from "@/features/dictation/components/mic-button";
 
 interface Props {
@@ -16,20 +17,14 @@ export const DictationGroup: FC<Props> = ({ editor, color, iconSize }) => {
   const workspace = useAtomValue(workspaceAtom);
   const streamingDictation =
     workspace?.settings?.ai?.dictationStreaming === true;
+  // Cause-specific reason the mic is unavailable (published by the page editor).
+  const dictationAvailability = useAtomValue(dictationAvailabilityAtom);
   // Caret snapshot taken when dictation starts (where the first segment lands).
   const rangeRef = useRef<{ from: number; to: number } | null>(null);
   // Running insertion point: after each inserted segment we remember the caret
   // end so the NEXT segment appends right after it, contiguously, regardless of
   // where the user's caret currently is. Null until the first segment lands.
   const insertPosRef = useRef<number | null>(null);
-  // editor.isEditable is a mutable, non-reactive field — read it via
-  // useEditorState so the mic re-enables when the body flips to editable after
-  // collab sync (otherwise it stays stuck disabled). Mirrors the body's own
-  // reactive read.
-  const isEditable = useEditorState({
-    editor,
-    selector: (ctx) => ctx.editor?.isEditable ?? false,
-  });
 
   const handleStart = () => {
     const { from, to } = editor.state.selection;
@@ -88,7 +83,8 @@ export const DictationGroup: FC<Props> = ({ editor, color, iconSize }) => {
       streaming={streamingDictation}
       onStart={handleStart}
       onText={handleText}
-      disabled={!isEditable}
+      disabled={!editor.isEditable}
+      unavailableReason={dictationAvailability.reason ?? undefined}
       color={color}
       iconSize={iconSize}
     />