Recover retained phase-goal continuations

[yvette-carlisle]

Summary

• recover stalled retained phase-goal lanes into continuation when there are no blockers or decision requests
• keep retry/repo-gate-owned dirty worktrees out of generic manual-attention projection
• update runtime/lane-control docs and regression coverage for retained phase-goal recovery

Validation

• cargo make fmt
• cargo make lint-fix
• cargo make test (1170 passed, 1 skipped)

Fixes XY-956