Proposal: explicit current-window audio capture for the media visualizer

[John-Ryan21337]

The Club media workspace includes an explicit audio-analysis capture path. The current Cafe adoption stack has the streaming/local players and bundled visualizer engine, but no renderer action for display-audio capture.

Proposed incremental drafts:

• Native prerequisite: bind Electron display-media requests to a visible, focused, exact trusted Cafe main frame after a user gesture. Grant only that frame's audio/video, with session-owner cleanup. This is not a system-wide loopback grant or native source picker.
• Renderer follow-up: an explicit Start/Stop action, immediate disposal of video tracks, session-only audio, cancellation on source/environment/visibility changes, and the existing analyser/visualizer. Browser builds may use their browser's source chooser; desktop wording must state the narrower current-Cafe-window scope.

No microphone fallback, recording, audio upload, account/session access, or automatic capture. Validation uses generated synthetic content in a separate process/profile, plus deterministic lifecycle and authority tests. Live YouTube/Spotify audio and platform combinations remain separately qualified.

Prerequisites: desktop renderer ownership PR75, streaming player fork PR87, local player fork PR90, and visualizer issue101. Large activation drafts will be stacked in the fork so each diff is reviewable.

[John-Ryan21337]

Native prerequisite published as incremental draft Club PR111, head2a82499fe3beeb305b0b102cfaeacc60b6cf8256, atop exact Cafe IPC PR75/cadc2e7f.

All required formatting/lint/types, full repository tests (4046 passed, five existing skips) and forced desktop build passed. Independent review and an isolated Electron42.5.1 synthetic native-click probe verified exact current-frame audio/video stream admission and track stop. No live player/account/audio was used. The renderer Start/Stop action and analysis integration remain the next draft; this prerequisite does not activate capture by itself.

[John-Ryan21337]

The renderer follow-up is published as incremental draft Club #115, exact 6d187c5cde8e0878231b6a208cc39732e8d2eeb1, atop the exact merge of native #111 and visualizer #112 (6b4f2eb6). It adds explicit Settings Start/Stop, player stop status, exact source/connection ownership and late chooser cleanup. All required checks and the forced desktop build passed, including 350 Chromium tests.

The draft includes an inspected 6.4-second synthetic recording through the real controls, analyser and GPU renderer. It does not claim live service audio, a real browser chooser or cross-platform audio qualification. Matrix music-color integration remains separate.

日本語：画面側の追加差分を上記 #115 として公開しました。前提は #111 と #112 の正確な統合です。明示的な開始・停止、接続とソースの所有権、遅れて返る結果の解放を追加し、必要な検査と強制ビルドは成功しました。動画は合成入力による実コンポーネントの検査であり、実サービスや他 OS の音声取得を確認したという意味ではありません。