feat: add offline meeting transcription milestone 1

[altic-dev]

Milestone 1

Adds the complete offline-first meeting transcription slice behind the new Meeting tab.

Included

• Online meeting capture with separate system-audio and microphone tracks
• In-room microphone-only capture
• Saved first-visit meeting setup with a compact Meeting Settings sheet
• Stable app and microphone reconciliation without silently switching unavailable saved sources
• Durable sessions, chunk manifests, recovery, and idempotent stopping
• Offline English transcription through the shared ASR executor
• Speaker diarization, session-wide speaker matching, and conservative You attribution
• Recording state and Stop Recording as the first menu-bar action
• Result, failure, retry, reveal, and permission states
• M1 model, coordinator, recovery, settings, and speaker-identity test coverage

Validation

• SwiftFormat
• SwiftLint strict: 0 violations across Sources
• Focused test target compiles with build-for-testing
• Private Fluid Intelligence Release build, install, and code-sign verification
• Installed-app visual scan of the Meeting page and saved Settings sheet
• Independent architecture and persistence review
• Independent UX and accessibility review
• XCTest execution: the app-hosted test process stalled before workers started; stopped without running tests
• Real online dual-track and in-room microphone capture
• Full keyboard, VoiceOver, permission, resize, and menu-bar scan
• Quit/interruption/device-change stress verification

Known proof boundary

• No manual Debug app run was performed.
• Real capture requires explicit microphone/screen-recording permission and consent.
• Multilingual Parakeet currently auto-detects because its provider API has no forced-language option; M1 UI remains English-only.
• Real-speaker cross-chunk identity quality still needs capture validation.

Draft until the unchecked M1 runtime gates are proven.

[github-actions]

The PR Policy check is blocking this PR because required template information is missing.

Please update the PR description with:

• Description
• Type of Change
• Related Issue or Discussion
• Testing
• Screenshots / Video

Visual files detected:

• Sources/Fluid/ContentView.swift
• Sources/Fluid/Persistence/SettingsStore.swift
• Sources/Fluid/Services/MenuBarManager.swift
• Sources/Fluid/UI/FileTranscriptionView.swift
• Sources/Fluid/UI/MeetingTranscriptionView.swift

Screenshots or video are required for UI, UX, settings, onboarding, overlay, menu bar, or visual behavior changes. If this PR has no visual changes, check the no-visual-change box in the template.

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