fix(chat): ignore a stale voice recognizer's async callbacks after restart

[pedrofrxncx]

Bug found while reading recently-touched apps/web/src/hooks/use-voice-input.ts (churned by #6451).

Failure scenario: cancelRecording() calls recognitionRef.current?.abort() but does not null out the ref, and startRecording() right after creates a new SpeechRecognition instance, reassigning recognitionRef.current. Browsers (Chrome) resolve abort() asynchronously as an error event with error: "aborted" — so the old, already-cancelled recognizer's onerror can fire after the new one is already recording. Its handler unconditionally does isRecordingRef.current = false; recognitionRef.current = null; setStatus(...), which kills the ref to the live recognizer and flips the UI status back to idle/permission-denied mid-recording. The same stale-closure issue affects onend, which could restart a dead recognizer instance that no longer holds the mic session.

Fix: each handler now checks recognitionRef.current !== recognition and bails if the callback belongs to a superseded instance — the same pattern already used to distinguish the live session from historic ones.

Regression test: use-voice-input.test.ts — starts recording, cancels, restarts (second SpeechRecognition instance), then fires the first instance's onerror({error: "aborted"}). Before the fix this drops status to idle even though the second recognizer is still recording; after the fix status stays recording. Verified the test fails on the pre-fix code (git stash the source file, rerun) and passes after.

To confirm: bun test apps/web/src/hooks/use-voice-input.test.ts

Checked locally: bun run fmt, cd apps/web && bunx tsc --noEmit (no new errors), bunx oxlint on both changed files (0 warnings/errors), and the targeted test file above. Full CI covers the rest.

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Summary by cubic

Prevents stale SpeechRecognition callbacks from affecting the current session after a restart. Previously, a cancelled recognizer’s late onerror("aborted") or onend could null out the live recognitionRef, flip status from recording, or restart a dead instance; now those callbacks are ignored if they don’t belong to the current recognizer.

• Handlers in use-voice-input.ts early-return when recognitionRef.current !== recognition.
• Adds a regression test that cancels, restarts, then fires the old instance’s onerror("aborted"), asserting status remains recording.

^{Written for commit 52cec91. Summary will update on new commits.}