#32084 fix(measure): cef-embedder.sh runs the fork's embedder tests on a writable copy of the CEF dist

Summary

The fleet's CEF embedder step (scripts/measure/cef-embedder.sh) ran no case against a seeded CEF build. On 2026-11-02 steps 6d191ccbefe7ed7c11e80bad and 100ec79aad999f8be34bba21 (aws-m4pro-8, cef-154.0.34-cmux.42 arm64) printed cmux-embedder: 0/14 passed with no ==> case line, then the worker's cleanup failed with permission denied on the copied framework's locale.pak.

Cause: the worker seeds $CMUX_CI_CEF_DIR read-only. The fork's test-cmux-embedder.sh copies the framework into its test app and re-signs that copy, with stderr sent to /dev/null. So codesign failed on the read-only copy and the runner stopped under set -e before any case.

This blocks the CEF crash release cef-154.0.34-cmux.42. Its embedder case parent-dealloc-hidden is the test for the CmuxParentViewTracker abort (STATUS item 6061).

Change:

• The runner runs on a writable copy of the dist (cp -R, then chmod -R u+w).
• On macOS the wrapper signs the copy first, as the runner does, with stderr shown. A failure then names its cause.
• A runner that stops before its first case is named in the summary.
• The work dir is made writable on exit, so the worker's step cleanup can remove it.
• Test seam: CMUX_EMBEDDER_INPUT_DIR takes the test-source archive from a local dir.

Testing

bash scripts/measure/tests/cef-embedder.test.sh uses a read-only dist and a fake runner that needs a writable framework copy, as the real one does.

• Red at ed2acc9c9e4 (test only): cmux-embedder: 0/2 passed, then FAIL: a run on a read-only dist ran no case.
• Green at 4d0b46e18b2: cef-embedder: ok, 5 of 5 runs.

Observed / Not run

• Observed: the red and the 5 greens above, on cmux-orchestrator-1 (Linux). The prepush gate found no new violations.
• Not run: the macOS codesign branch is not covered by the test (no codesign on Linux). There is no fleet run of the fixed script yet: the controller runs this measurement script only at a commit on feat-cmux-next, so the real embedder runs (red on cmux.41, green on cmux.42) come after this lands.

Changelog

none

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Summary by cubic

Fixes the CEF embedder measurement script so it runs the fork's embedder tests against the seeded dist instead of stopping silently before any case.

• Runs the runner on a writable copy of the dist (cp -R, chmod -R u+w), since the seeded $CMUX_CI_CEF_DIR is read-only and the runner re-signs its framework copy with stderr hidden, failing under set -e before any case ran.
• On macOS, signs the framework copy first with stderr shown so a codesign failure names its cause.
• Names a runner that stops before its first case in the summary instead of only printing 0/N passed.
• Makes the work dir writable on exit so the worker's step cleanup can remove it (it previously failed with permission denied on locale.pak).
• Adds CMUX_EMBEDDER_INPUT_DIR as a test seam to source the test archive from a local directory.

Adds scripts/measure/tests/cef-embedder.test.sh, which reproduces the read-only dist with a fake runner and covers both a full run and an early stop. The macOS codesign branch is not covered by the test (no codesign on Linux).