Add verify diagnostics CLI with validation tests

[MRhuang1106]

Summary

Adds tools/verify_diagnostics.py, a CLI for validating diagnostic JSON reports and referenced .logd artifacts before opening a PR.

Changes

• Adds argparse CLI support for diagnostic report validation.
• Supports verbose output, JSON output, and threshold checks.
• Validates diagnostic JSON structure, module counts, module status values, logd path shape, chunk ordering, decrypt command presence, and missing artifact references.
• Adds defensive subprocess handling for missing executables, timeouts, non-zero exits, and OS errors.
• Adds focused unittest coverage for valid reports, structural errors, threshold failures, JSON CLI output, and subprocess error handling.
• Adds diagnostic artifacts under diagnostic/ for this PR.

Testing

python -m unittest discover -s tests
Ran 6 tests
OK

Also attempted local diagnostic build commands on Windows:

python build.py
python build.py -m backend

The full build could not complete in this environment because required toolchains such as npm/cargo/git are not installed. The captured local diagnostic output is committed as:

• diagnostic/build-b58b0052.json
• diagnostic/build-b58b0052.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

[MRhuang1106]

Added the requested diagnostic artifacts to PR #14: diagnostic/build-b58b0052.json and diagnostic/build-b58b0052.logd. Unit tests pass locally with python -m unittest discover -s tests. Full python build.py was attempted, but this Windows environment is missing several required toolchains, so the diagnostic files include the captured local failure output.