fix: tighten skill generation policy prompts

[RerankerGuo]

Fixes #1380.

Summary

• Tighten the skill creation evaluator prompt so low-reuse tasks are rejected before skill generation.
• Add explicit filters for simple tool installation plus basic config, exploratory revert/abandon outcomes, and discussion/comparison-only outputs.
• Add the requested experienced-developer self-check before returning shouldGenerate=true.
• Reinforce generator guidance to prefer reusable patterns, abstract diagnostic mistakes, and keep project/version-specific details as examples unless required.
• Add a prompt-policy regression test for the new evaluator and generator guidance.

Validation

• Direct Node prompt-policy string check passed.
• Attempted: npm test -- --run tests/skill-prompt-policy.test.ts; blocked because vitest is not installed in this worktree.
• Attempted: npm run build; blocked because tsc is not installed in this worktree.
• Attempted: make format; blocked because poetry is not installed in this environment.

[Memtensor-AI]

Automated Test Results: PASSED

Cloud test-engine full-audit rerun against dev-v2.0.22 completed successfully after clearing the cloud workspace disk.

• Run: tr-1eb15b94-4a0 on cloud test-engine 10012
• memos_local_openclaw/unit: 2 passed, 0 failed, 0 skipped

Manual code review is still required before merge.