feat(hooks): add post_tool MCP hook — auto-scan file after AI write (closes #47 phase-1)

[Wolfvin]

Summary

Implements Phase 1 of issue #47: MCP post_tool hook.

What changed

• New: scripts/mcp_hooks/init.py, scripts/mcp_hooks/post_tool.py
• Modified: scripts/mcp_server.py (HookManager class)
• Default: disabled (opt-in via .codelens/hooks.json)
• Non-blocking: ThreadPoolExecutor

Verification

• Tests: 825 passed, 87 skipped, 1 pre-existing failure (test_hybrid_engine — unrelated to this PR); 38 new tests added in tests/test_mcp_hooks.py — all passing.
  Closes [FEATURE] MCP hooks — auto-trigger scans on AI write / dep change / task end (extracted from #23) #47

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[sonarqubecloud]

Quality Gate failed

Failed conditions
D Security Rating on New Code (required ≥ A)

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