Personal and project dictation vocabulary #1933

User outcome

Supply recognition hints for repository names, technical words and chosen spellings. Keep recognition hints distinct from post-transcription corrections.

Current scope

No vocabulary/dictionary settings or hint path was found in the speech pipeline. Verify support separately for local NeMo and each cloud provider before exposing a setting.

Acceptance criteria

• Add ordered preferred vocabulary at personal/project scope with explicit precedence.
• Use provider-supported recognition hints; keep aliases and post-transcription corrections separate.
• Preserve hints during supported streaming/retry paths and retain existing behavior for unsupported engines/languages.

Verification

Add focused behavior coverage for the changed path, run relevant checks and record any unverified platform/provider behavior. Do not alter real user credentials or settings during tests.

Tracked by #1926. Implementation status is separate from merge status.