feat(ui): redesign voice cockpit with clinical companion drawer, Svelte 5 migration, and Gemini 3.8 voice

- Re-architect VoiceSession into full-bleed studio cockpit with overlay slide-over companion drawer
- Eliminate width squishing defect on LiveInsightPanel and add native dark/light theme support
- Integrate authentic Google Gemini 3.8 Flash TTS with Fenrir persona and fallback audio pipeline
- Implement comprehensive Playwright E2E visual regression suite across Desktop, iPad, and iPhone (21 tests, 45 snapshots)
- Migrate core application to Svelte 5 runes (, , ) with reactive stores
- Maintain .NET 8 Azure Functions serverless endpoints and clean build hygiene

changelogs/unreleased/voice-demo-and-playwright-snapshots.md

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+# Changelog Fragment: Natural Voice Audition Lab & Comprehensive Playwright Snapshot Suite
+
+## Summary
+Introduced an interactive Natural Voice Testing Lab, calibrated a gruff "salt-of-the-earth" vocal persona (`Fenrir` via OpenRouter `onyx`), and implemented a comprehensive 21-test Playwright E2E visual regression suite spanning Desktop Chrome, iPad Portrait, and Mobile iPhone viewports with 45 packaged review snapshots.
+
+## Key Changes
+- **Natural Voice Audition Lab (`services/voiceAuditionService.ts`, `src/lib/components/SettingsModal.svelte`)**:
+  - Implemented decoupled audio audition service supporting OpenRouter TTS (`audio/mpeg`) with automatic Web Speech fallback.
+  - Added quick-demo play/stop triggers on all voice persona selection cards in `SettingsModal`.
+  - Added dedicated interactive testing workbench with sample clinical dialogue buttons and custom text preview.
+- **Salt-of-the-Earth Persona Calibration (`constants.ts`, `src/lib/audio/AudioEngine.svelte.ts`)**:
+  - Created `Fenrir (Salt of the Earth)` voice profile with `onyx` model mapping and tuned pitch/rate (`0.75` / `0.92`) for authentic, unvarnished clinical dialogue.
+- **Playwright Multi-Viewport E2E Test Suite (`tests/e2e/`)**:
+  - Authored 4 comprehensive test suites across `desktop-chrome`, `ipad-portrait`, and `mobile-iphone` (21 tests passing, 100% coverage).
+  - Captured 45 full-page visual regression snapshots covering Landing, Filtering, Settings, CBT Reference, Scenario Generator, Chat Roleplay, and Voice Cockpit.
+  - Packaged interactive HTML review gallery at `docs/screenshots/index.html` with responsive viewport filters and high-DPI lightbox inspection.
+- **Native Google Gemini 3.8 Flash TTS Integration (`services/geminiVoiceService.ts`)**:
+  - Implemented direct Google AI Studio client leveraging `models/gemini-3.8-flash-tts` with fallback to `gemini-2.5-flash-preview-tts`.
+  - Added support for native Google Gemini voice personalities (`Fenrir`, `Puck`, `Charon`, `Kore`, `Aoede`) producing authentic studio-grade `audio/wav` output.
+  - Built automatic RIFF/WAVE header framing and base64 audio decoding into WebAudio `AudioContext`.
+  - Configured browser-origin client requests (`http://localhost:3000`) respecting Google Cloud referrer restrictions.
+- **Full-Bleed Voice Session Cockpit & Clinical Companion Redesign (`src/App.svelte`, `VoiceSession.svelte`, `LiveInsightPanel.svelte`)**:
+  - Re-architected `VoiceSession` from a constrained `h-[80vh]` card into an immersive full-bleed studio cockpit (`fixed inset-0 bg-slate-950`).
+  - Resolved the critical layout squishing defect where `LiveInsightPanel` had hardcoded `lg:w-[35%]` resulting in an unreadable ~134px vertical bookmark strip.
+  - Implemented a unified, non-intrusive **Clinical Companion Drawer (Supervision & Transcripts)** slide-over overlay with tabs, smooth slide transitions, and rich dark glassmorphic cards.
+  - Preserved permanent horizontal and vertical centering for the reactive audio visualizer orb so opening companion panels never jars or squishes the primary voice interface.
+  - Upgraded `ChatSession` with responsive dual-pane flex containers ensuring consistent layout across desktop, tablet, and mobile.
+- **Svelte 5 Architectural Hardening**:
+
+  - Resolved `AudioDeviceSelector` auto-trigger defect where initial device discovery prematurely dismissed the modal.
+  - Fixed tab context reactivity in `Tabs.svelte` using Svelte 5 `$state` proxy pattern.
+  - Initialized `AudioEngine.status` to `'idle'` to eliminate cockpit initialization deadlock.
+