Add ANCP compact signal layer

[Rtx09x]

Summary

• adds compact raw-text rendering for ANCP result documents with token budget support
• saves raw native stdout/stderr under .ancp/runs/<run-id>/ and records signal metrics in result.check
• adds ancp enable, disable, uninstall, and status for reversible Windows/global shim management
• documents the compact signal layer and updates the CLI contract

Verification

• PYTHONPATH=src pytest -q
• PYTHONPATH=src python tools\verify_repo.py
• PYTHONPATH=src python tools\audit_contracts.py
• PYTHONPATH=src python -m compileall -q src tests tools
• PYTHONPATH=src python -m ancp.cli validate .ancp\last-check.json .ancp\bug-corpus
• python -m build
• python -m twine check dist\*
• isolated live shim smoke: temp auto-compact Python shim produced compact ANCP output, preserved exit code 1, wrote .ancp/last-check.json, and saved raw native output under .ancp/runs/.../native.log