Address review findings in the app, server and tests

- app: startup shell, python and ssh probes run asynchronously so a slow
  shell profile can't freeze the window; PATH comes from the user's real
  login shell and a failed lookup isn't cached; a server that never
  answers is killed; the setup offer runs once per launch, only after the
  UI loads, and decides from HostName alone; connect.sh is started through
  `env ... zsh` so it works whatever the login shell is.
- server: volume validates the level before muting or changing anything.
- Steam: null-safe install-manager fields, http.client errors caught in
  store ratings, price fallback when a sale has no final price.
- tests: server output kept for diagnosis, any startup error retried, and
  captures asserted non-cacheable.

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

docs/how-the-frame-works.md

@@ -43,7 +43,8 @@ Lepton (Android 11, podman container "lepton-dev") ← its own panel, app 305600
 | Lepton Development deletes every ADB-installed app when it exits (`clear_baked_app_data "non steamlaunch container"` in `…/common/Lepton/lepton`) unless `LEPTON_NO_CLEANUP` is set. | [apks.md](apks.md) |
 | Any APK can run as its own Lepton instance: run `…/common/Lepton/lepton waitforexitandrun -- app.apk` with `SteamAppId` set and `STEAM_COMPAT_DATA_PATH` under `~/.local/share/Steam`. Data persists and each gets its own container and panel. `frame/android/lepton-app.sh`, `ui/frame_android.py`. | [apks.md](apks.md) |
 | The Steam client runs with `-cef-enable-debugging`, so its UI answers Chrome DevTools on loopback `127.0.0.1:8080`. The `SharedJSContext` page has `appStore` (owned apps), `downloadsStore` and `SteamClient.*`. `steam steam://install/<appid>` over SSH installs an owned game; when the options dialog shows (state 7), `SteamClient.Installs.ContinueInstall()` accepts it. **Verified 2026-09-25** with Balatro and Broforce. The Frame rating is `steam_hw_compat_category_packed >> 8 & 3`. | [steam-games.md](steam-games.md), `ui/frame_steam.py` |
-| Chromium Flatpak 154 has **no immersive WebXR**: `navigator.xr` exists, but `isSessionSupported("immersive-vr")` returns `false`. Web VR180 players (DL8/DeoVR embeds) still play video inline as a flat, pannable view, and their VR button opens a tab on immersiveweb.dev. Forcing it doesn't help. `--enable-features=OpenXR,WebXR --force-webxr-runtime=openxr`, with `/opt/steamvr` and `XR_RUNTIME_JSON` exposed to the Flatpak, still returns `false`. The aarch64 Linux binary has no OpenXR code at all (no `xrCreateInstance`, no loader), even though `chrome://flags` lists `#webxr-runtime` → OpenXR. To watch in 3D, use a native player. Started with `--remote-debugging-port=9222`, Chromium answers DevTools on loopback. **Verified 2026-09-25**, BUILD_ID 20260922.6101926. | Web video, [panels.md](panels.md) |
+| Chromium Flatpak 154 has **no immersive WebXR**: `navigator.xr` exists, but `isSessionSupported("immersive-vr")` returns `false`. Web VR180 players (DL8/DeoVR embeds) still play video inline as a flat, pannable view, and their VR button opens a tab on immersiveweb.dev. Forcing it doesn't help. `--enable-features=OpenXR,WebXR --force-webxr-runtime=openxr`, with `/opt/steamvr` and `XR_RUNTIME_JSON` exposed to the Flatpak, still returns `false`. The aarch64 Linux binary has no OpenXR code at all (no `XR_RUNTIME_JSON`, `xrGetInstanceProcAddr` or loader strings), even though `chrome://flags` lists `#webxr-runtime` → OpenXR. **Why (verified against source 2026-09-25):** M154 is the first release that compiles OpenXR on Linux (`enable_openxr` includes `is_linux`, `checkout_openxr` is true in Flathub's tarball, and Flathub's GN args don't turn it off). But `content/services/isolated_xr_device/xr_runtime_provider.cc` only creates an OpenXR device under `ENABLE_OPENXR && IS_WIN`, on 154, 155 and `main`. Nothing on Linux calls the OpenXR code, so the linker drops it. The missing pieces are two unmerged Gerrit CLs (bug 506004811): [8132979](https://chromium-review.googlesource.com/c/chromium/src/+/8132979) wires the provider on Linux (with `kOpenXR` still off by default, so it needs `--enable-features=OpenXR`), and [8441736](https://chromium-review.googlesource.com/c/chromium/src/+/8441736) runs the XR service in a sandbox that allows SteamVR's sockets. The Frame does have an aarch64 runtime: `~/.config/openxr/1/active_runtime.json` → SteamVR `bin/linuxarm64/vrclient.so`. To watch in 3D, use a native player, or a Chromium built with those two CLs. Started with `--remote-debugging-port=9222`, Chromium answers DevTools on loopback. **Verified 2026-09-25**, BUILD_ID 20260922.6101926. | Web video, [panels.md](panels.md) |
+| **DeoVR (Steam app 837380, Windows/Unity) runs immersively** under Proton ARM64 + FEX: Unity's OpenVR XR plugin finds `OpenVR Headset(Steam Frame)` and the `frame_controller`, the GPU shows as Turnip Adreno 750, and AVPro Video decodes through `MF-MediaEngine-Hardware`. It played 7680×3840 and 8192×4096 H.265 VR180 SBS streams in dome/fisheye mode (`FirstFrameReady`). Unity's own `VideoPlayer` (used for grid thumbnails) fails with `0xc00d36bb`, so thumbnail previews stay blank. The first launch takes about 45 s (`ComputeShaders: InitAsync`). Log: `compatdata/837380/pfx/drive_c/users/steamuser/AppData/LocalLow/Deo VR/Deo VR/Player.log`. **Verified 2026-09-25**, BUILD_ID 20260922.6101926. | [vr-video.md](vr-video.md) |
 | Power actions need `sudo`, which asks for the Developer Mode password over SSH. | Frame Control's power buttons |
 
 ## Debug recipes