Headset programs rebuilt from the current source; releases can't ship them stale

The committed frame/payload still had Frame Home from Oct 21, which opens baked
scenes up to v13, while Studio has saved v14 since wall spots were removed: every
environment saved and sent from a release failed on the headset with "baked scene
from a different Frame Studio version".

- frame/payload: frame-home and fenv-tool rebuilt on the Frame from this source
  (byte-identical to what is installed there now).
- frame/payload/SOURCE + scripts/frame-payload.sh: records the source the headset
  programs were built from; CI checks it in the installer job and in the release
  job, so nothing is published beside an outdated headset build.
- fenv-tool version prints the newest baked scene it opens; Studio asks before
  Send to Frame and Calculate Best Settings and says to update Frame Home instead
  of sending a file the headset can't open.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -104,6 +104,8 @@ jobs:
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v4
+      - name: Headset programs match the source
+        run: sh scripts/frame-payload.sh check
       - name: Package
         run: sh scripts/build-studio.sh frame-home
       - uses: actions/upload-artifact@v4
@@ -134,6 +136,10 @@ jobs:
       - uses: actions/checkout@v4
         with:
           path: src
+      # Every download carries frame/payload: none is published beside headset programs older than the source
+      # (Studio would save environments the headset can't open).
+      - name: Headset programs match the source
+        run: sh src/scripts/frame-payload.sh check
       # What Frame Studio (studio/updater.h) and the headset's Environments panel check for updates: this commit,
       # Frame Home's identity (a hash of the headset programs, the same one the panel works out for what's installed)
       # and the files in this release.