🛡️ Sentinel: [security enhancement] Harden unit test gate and fix telemetry bug

[heidi-dang]

🚨 Severity: MEDIUM
💡 Vulnerability: Environment variable leakage and missing sandbox escape checks in the unit test gate script.
🎯 Impact: Sensitive keys (like OPENAI_API_KEY) could be exposed to generated code being tested. Basic sandbox escapes using __subclasses__ were also possible.
🔧 Fix:

• Implemented a strict environment variable allowlist (PATH, PYTHONPATH, LANG, PYTHONIOENCODING) for the test subprocess in scripts/03_unit_test_gate.py.
• Added __subclasses__, __globals__, and __builtins__ to the DANGEROUS_PATTERNS list.
• Used textwrap.indent to ensure injected code is correctly formatted in the test wrapper.
• Fixed a NameError in heidi_engine/telemetry.py caused by a redundant and broken cache check using an undefined variable.
  ✅ Verification: Created and ran a custom verification script verify_hardening.py to confirm that sensitive environment variables are not leaked and dangerous patterns are blocked. Ran the full test suite with pytest and confirmed all 21 tests passed.

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PR created automatically by Jules for task 17690827714301133543 started by @heidi-dang

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[gemini-code-assist]

Code Review

This pull request focuses on security hardening for the unit test gatekeeper by implementing environment isolation and blocking Python introspection attributes to prevent sandbox escapes. It also removes a state cache optimization in the telemetry module and updates the security sentinel log. Feedback suggests refining the environment variable allowlist by removing redundant keys and ensuring cross-platform compatibility through case-insensitive key matching.

[gemini-code-assist]

The PYTHONPATH key in allowed_env_keys is redundant because it is explicitly overwritten on line 269. Removing it from the allowlist improves clarity and ensures that the host's PYTHONPATH is intentionally ignored in favor of the isolated temp_dir. Additionally, consider moving allowed_env_keys to a module-level constant to avoid recreating the set on every function call.

Suggested change

	allowed_env_keys = {"PATH", "PYTHONPATH", "LANG", "PYTHONIOENCODING"}
	allowed_env_keys = {"PATH", "LANG", "PYTHONIOENCODING"}

[gemini-code-assist]

Environment variable keys can be case-insensitive on some platforms (like Windows). The current set lookup is case-sensitive, which might cause essential variables like Path (instead of PATH) to be filtered out, potentially breaking the subprocess execution. Using k.upper() for the check ensures cross-platform robustness.

Suggested change

	safe_env = {k: v for k, v in os.environ.items() if k in allowed_env_keys}
	safe_env = {k: v for k, v in os.environ.items() if k.upper() in allowed_env_keys}