Add approval testing: verify artifacts against approved baselines

[JE-Chen]

Testing batch — golden-master / snapshot testing for any artifact. Full layers + tests + EN/Zh v35 docs + README.

Feature (utils/approval, pure-stdlib)

• verify_artifact(name, content, approvals_dir, extension) compares produced content (str or bytes) to a stored <name>.approved.<ext> baseline. On match: pass, stale received cleared. On mismatch/missing baseline: writes <name>.received.<ext> for review and returns match=False (status mismatch/new). approve_artifact promotes a reviewed received file to the baseline; pending_artifacts lists names awaiting approval. Names are path-traversal-checked.
• Works for rendered text, JSON, OCR output, screenshot bytes — complements pixel diffing with a review-gated baseline committed alongside the test.
• Executor AC_verify_artifact / AC_approve_artifact / AC_pending_artifacts; MCP ac_*; Builder under Testing.

Verification

• 10 tests pass (new→received, approve→match, mismatch re-writes received, verified clears stale received, bytes/png, approve-without-received raises, path-traversal rejected, executor round-trip, wiring); ruff clean; radon no CC≥C; bandit clean; PySide6-free.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 45 complexity · 0 duplication

Metric	Results
Complexity	45
Duplication	0

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud