Gate HRX pin updates on long-prompt validation

[Copilot]

Short-prompt and backend-op checks missed an HRX regression that returned end-of-text on a 4.7K-token Qwen3-0.6B prompt. Require pin-specific long-prompt validation before an HRX submodule update is accepted.

• Probe: Add tests/hrx_long_prompt.py to warm up llama-server, confirm the prompt is at least 4,700 tokens, and require the buried-code answer 7341.
• Pin gate: CI rejects a changed HRX pin unless its full commit matches config/hrx-long-prompt-validated-pin.config. Update that record only after validating the proposed pin on Strix Halo:

  python3 tests/hrx_long_prompt.py

• Documentation and coverage: Describe the validation procedure and add focused tests for the pin gate and probe prompt.

• Fixes hrx-system 4ba76c18eafe: Qwen3-0.6B returns end-of-text at once on a 4.7K-token prompt (98d05d94 answers) #369

[github-actions]

PR Reviewer Guide 🔍

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🎫 Ticket compliance analysis ✅ 369 - PR Code Verified Compliant requirements: Fix the regression where Qwen3-0.6B returns end-of-text at once on a 4.7K-token prompt with HRX backend Gate HRX pin updates on long-prompt validation Add a probe test to verify correct behavior on long prompts Update documentation to describe the validation procedure Requires further human verification: Verification that the proposed hrx-system pin passes the long-prompt test on Strix Halo

⏱️ Estimated effort to review: 3 🔵🔵🔵⚪⚪

🧪 PR contains tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Potential Timeout Issues The hrx_long_prompt.py script uses a 300-second timeout for HTTP requests. In the case of a regression or performance degradation, this timeout may not be sufficient to complete the long-prompt test, potentially masking issues. Consider making the timeout configurable or increasing it to ensure robustness. with urllib.request.urlopen(request, timeout=300) as response: return json.load(response) Validation Error Message Clarity The error message in hrx_validation_error function could be more specific about what constitutes a valid commit. While it mentions running tests/hrx_long_prompt.py, it doesn't clearly state that the commit must be validated on Strix Halo before being accepted. def hrx_validation_error(path, new, validated): if path == HRX_PATH and new != validated: return (f"hrx-system pin {new[:12]} has not passed the long-prompt check; " f"run tests/hrx_long_prompt.py on Strix Halo and update {HRX_VALIDATED_PIN}") return None