feat: Discord widget — embedded Discord web with voice + screen share

[nishant]

Summary

• New Discord widget: the real discord.com web app embedded in an Electron <webview> on a dedicated persist:discord partition — servers, DMs & group chats, replying, voice channels, and screen sharing with an in-widget screens/windows picker. Zero setup: no Discord application, no keys — log in once inside the widget; the session survives restarts.
• Why embed instead of a custom client: official Discord APIs cannot do user-account DMs/messaging/voice, the local RPC API is private-beta with no send-message command, and a user-token self-bot violates ToS (ban risk). Embedding the web app is the WebCord-proven, ToS-conformant path.

Main-process plumbing (apps/main/src/discord.ts)

• persist:discord session: full clean-Chrome UA (the Nishboard/x app token alone trips Discord's unsupported-browser wall) + permission request and check handlers (Discord gates notifications on the sync Notification.permission read), scoped to *.discord.com.
• Screen share: setDisplayMediaRequestHandler → desktopCapturer sources cross as data-URI thumbnails (discord:screenshare-* IPC, subscribe-while-mounted lifecycle, 60s deny timeout). Windows-only system audio via audio: 'loopback'; macOS shares video-only.
• Hardening: webviewTag: true on main + popout windows, gated by an app-wide will-attach-webview guard (https *.discord.com src only, URL-parsed — lookalike hosts rejected; preload/nodeIntegration stripped). Guest window.open/off-site navigations open the system browser.

Renderer

• Widget with loading shimmer, main-frame-only error card, mention badge from the guest title (N), Home/Reload/Sign-out header actions (sign-out clears the partition after an in-body confirm).
• WidgetShell grows opt-in keepMounted: collapsing Discord hides the body in an h-0 overflow-hidden wrapper instead of unmounting — voice keeps running (display:none kills a webview guest).
• macOS packaging: mac.extendInfo mic/camera usage strings (TCC would silently deny voice).

Tests

• apps/main/src/discord.test.ts: UA shape, URL allowlist (incl. discord.com.evil.com rejection), permission matrix, capturer-source serialization.
• apps/renderer/.../lib.test.ts: title-badge parsing. Electron stub grew session/desktopCapturer/app.on.
• Full pnpm test / typecheck / lint green; dev boot smoke-tested.

Known caveats (documented in CLAUDE.md)

• Unpin / pop-out toggle / quit remounts the webview → an active voice call drops (login persists).
• Screen-share system audio is Windows-only; badge counts mentions/DMs only (Discord's (N) title prefix).

Manual verification checklist (needs a logged-in account)

• Pin the widget → Discord login renders → log in → relaunch → still signed in
• Join a voice channel → mic works, no permission popup
• Screen share → picker → stream visible to a second account; Cancel + timeout behave
• Collapse mid-voice → audio continues; expand repaints
• External chat link → system browser; DM while unfocused → native toast + badge
• Sign out → back to login; other widgets untouched; pop-out remounts signed-in

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