Report failed clean commands

[manusss2026]

/claim #1

Summary

Report failed clean commands from clean_module instead of treating every completed subprocess as a successful clean.

Changes

• Check clean_module subprocess return codes and return False for non-zero exits.
• Print the module name, exit status, and captured stdout/stderr when a clean command fails.
• Keep timeout and command-not-found failures non-crashing and visible to callers.
• Propagate clean failures through python build.py --clean with a non-zero exit code.
• Add tools/validate_clean_module.py to demonstrate successful clean, non-zero clean, and missing-command handling.
• Catch missing npm during the frontend prebuild install step so full diagnostic generation can finish in minimal environments.

Testing

• python tools/validate_clean_module.py -> passed.
• python -m py_compile build.py tools/validate_clean_module.py -> passed.
• python build.py -> ran and generated diagnostics. The build exited 1 because this Windows environment is missing toolchains such as cargo, npm, go, gcc/g++, cmake, make, javac, ruby, luac, and ghc; those failures are captured in the diagnostic metadata.

Diagnostic artifacts committed:

• diagnostic/build-5b7632ca.json
• diagnostic/build-5b7632ca-part001.logd
• diagnostic/build-5b7632ca-part002.logd
• diagnostic/build-5b7632ca-part003.logd

Checklist

• Relevant modules affected by these changes build locally
• Tests pass locally
• Diagnostic build log is committed in this PR
• Documentation has been updated, if applicable
• Configuration or schema changes are documented, if applicable
• No generated build artifacts are committed, except the required diagnostic build log
• Changes are scoped to the PR purpose and avoid unrelated cleanup
• Security, privacy, and error-handling implications have been considered

---

• I would like to request that my diagnostic build log is removed before merging

[benglezhenjun]

Please update the diagnostic metadata and rerun the validation. The current diagnostic JSON uses Windows backslash paths such as diagnostic\build-5b7632ca-part001.logd. Please regenerate diagnostics so diagnostic_logd uses repository-style forward slash paths, e.g. diagnostic/build-5b7632ca-part001.logd. Also ensure the GitHub Actions diagnostic check actually runs and passes before merge.

[manusss2026]

Updated, thanks for the heads-up.

Changes pushed in 829a070:

• build.py now emits repository-relative diagnostic paths with forward slashes via Path.as_posix().
• Regenerated diagnostics for ae53edae; metadata now points to diagnostic/build-ae53edae-part*.logd and the reassemble/decrypt commands use / separators.
• Removed the stale diagnostic/build-5b7632ca* bundle that contained Windows backslash paths.

Validation rerun:

• python -m py_compile build.py tools\validate_clean_module.py
• python tools\validate_clean_module.py
• python build.py generated the new diagnostic bundle; local module builds still fail on this Windows runner because the toolchain commands are not installed, but the diagnostic bundle generation completed successfully.