Enforce deletion-grade Crane migration scoring and CI gates

[Copilot]

Description

Crane could report migration_score: 1.0 from progress-oriented parity events without proving Python-vs-Go cutover readiness. This updates scoring so 1.0 requires every explicit cutover gate to pass.

• Score gates

  • Added cutover_gates and deletion_grade_ready.
  • Require Python reference, surface/help/functional/state parity, zero exceptions, Go/Python tests, and benchmarks.

• Hard failures

  • Reject empty or incomplete Go test event streams.
  • Package-level Go failures now block cutover scoring.

• CI/test hardening

  • Migration parity CI now gates completion on progress == 1.0 while preserving the invariant that migration_score == 1.0 requires deletion_grade_ready.
  • Crane score tests now provide a temporary Go build cache when HOME/GOCACHE are absent.

"cutover_gates": {
  "python_reference_required": true,
  "surface_parity": 1.0,
  "help_parity": 1.0,
  "functional_contracts": 1.0,
  "state_diff_contracts": 1.0,
  "known_exceptions": 0,
  "go_tests": "pass",
  "python_tests": "pass",
  "benchmarks": "pass"
}

Type of change

• Bug fix
• New feature
• Documentation
• Maintenance / refactor

Testing

• Tested locally
• All existing tests pass
• Added tests for new functionality (if applicable)

[mrjf]

@copilot fix tests

[Copilot]

@copilot fix tests

Fixed in 27d1868. The Crane score tests now provide a Go build cache even when HOME/GOCACHE are absent, and the migration parity workflow now gates completion on progress == 1.0 while preserving the invariant that migration_score == 1.0 requires deletion_grade_ready.

[github-actions]

Migration Benchmark Results

• Commit: 27d18681e093088a83dc632728dd95bec6c6eb3c
• Run: https://github.com/githubnext/apm/actions/runs/26586968423

Migration CLI Benchmark

Max allowed Go/Python median ratio: 5.00

Command	Python median	Go median	Go/Python	Result	Return codes
--help	0.4525s	0.0012s	0.00x	380.45x faster	{'python': [0], 'go': [0]}
--version	0.4267s	0.0011s	0.00x	373.21x faster	{'python': [0], 'go': [0]}
compile --help	0.4337s	0.0011s	0.00x	386.00x faster	{'python': [0], 'go': [0]}
install --help	0.4253s	0.0012s	0.00x	362.49x faster	{'python': [0], 'go': [0]}
pack --help	0.4256s	0.0012s	0.00x	365.03x faster	{'python': [0], 'go': [0]}
audit --help	0.4275s	0.0012s	0.00x	352.84x faster	{'python': [0], 'go': [0]}
init --yes	0.4279s	0.0013s	0.00x	329.96x faster	{'python': [0], 'go': [0]}