Mac in the headset: stream Mac windows and screens into the Frame as panels

Frame Control can now show any Mac window, or a whole screen, as its own
SteamVR panel on the Steam Frame (Tools -> Mac in the headset, macOS only).
Place it with the SteamVR dashboard; the laser clicks and scrolls, and the
Mac's own keyboard types.

- mac/frame-mac-view (Swift, no dependencies): ScreenCaptureKit capture per
  window or display, VideoToolbox H.264 with low-latency rate control (JPEG
  fallback), a loopback HTTP/WebSocket server, CGEvent/AX input playback,
  and a display-awake assertion while anyone watches.
- ui/frame_macview.py: starts the agent, runs an ssh -R tunnel with a
  supervisor that reopens it on the same port, and launches a Chromium app
  window per stream on gamescope's :0, tagged with STEAM_GAME for its own panel.
- Frame Control's key never leaves the Mac: viewers get single-use,
  per-source tickets and reconnect keys that Stop revokes.
- ui/mac-view.html: WebCodecs decode, keyframe recovery, pointer/wheel/keys back.
- Bundled in the Mac app build; tests/test_macview.py builds and drives the
  agent on macOS.

Verified on the Frame (build 20260925.6191901) with the test pattern: panel
in about 1.5 s, about 60 fps, Mac-to-window about 11-17 ms, tunnel recovery
in 4 s. Laser input and real window capture still need a person in the headset.

Also commits the other thread's first-party rule (steam-frame skill) and
the first-party options table in docs/streaming.md.

Reviewed by GPT-6 Astra (xhigh, read-only) over six rounds; all findings fixed.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

app/package.json

@@ -9,8 +9,8 @@
   "scripts": {
     "start": "env -u ELECTRON_RUN_AS_NODE electron .",
     "icon": "env -u ELECTRON_RUN_AS_NODE electron build/make-icon.js",
-    "dist": "node build/fetch-deps.js mac arm64 && electron-builder --mac --arm64 --publish never",
-    "dist:dir": "node build/fetch-deps.js mac arm64 && electron-builder --mac --arm64 --dir",
+    "dist": "sh ../mac/frame-mac-view/build.sh && node build/fetch-deps.js mac arm64 && electron-builder --mac --arm64 --publish never",
+    "dist:dir": "sh ../mac/frame-mac-view/build.sh && node build/fetch-deps.js mac arm64 && electron-builder --mac --arm64 --dir",
     "dist:linux": "node build/fetch-deps.js linux x64 arm64 && electron-builder --linux --x64 --arm64 --publish never",
     "dist:win": "node build/fetch-deps.js win x64 && electron-builder --win --x64 --publish never"
   },
@@ -105,9 +105,19 @@
         "dmg",
         "zip"
       ],
+      "extraResources": [
+        {
+          "from": "../mac/bin",
+          "to": "mac/bin",
+          "filter": [
+            "frame-mac-view"
+          ]
+        }
+      ],
       "extendInfo": {
         "NSAppleEventsUsageDescription": "Frame Control opens Terminal for SSH sessions and for power actions that need the Developer Mode password.",
-        "NSLocalNetworkUsageDescription": "Frame Control connects to your Steam Frame over SSH on the local network."
+        "NSLocalNetworkUsageDescription": "Frame Control connects to your Steam Frame over SSH on the local network.",
+        "NSScreenCaptureUsageDescription": "Frame Control shows your Mac's windows and screens inside the Steam Frame when you ask it to."
       },
       "artifactName": "Frame-Control-mac-${arch}.${ext}"
     },