Integrate safe missing-inventory pruning

[chubes4]

Summary

• integrate bounded missing-worktree inventory pruning into safe cleanup
• omit unset optional Ability inputs and preserve continuation cursors correctly
• revalidate path, PR, unpushed, ownership, and provenance protections atomically at deletion
• preserve malformed, external, ambiguous, and owner-managed records
• add production-shaped pagination and concurrent-update regressions

Closes #996.

Verification

• php tests/worktree-inventory-prune-missing.php
• php tests/workspace-safe-cleanup-orchestrator.php
• workspace compact-output and safe-cleanup schedule suites
• PHP syntax/static checks
• git diff --check

Changed-only PHPCS still reports legacy file-scoped alignment findings whose baseline fingerprints shift with edited line numbers; behavior and static-analysis gates pass.

AI Assistance

• Model: OpenAI openai/gpt-5.6-sol
• Tool: OpenCode
• Used for: implementation, deletion-race analysis, regression tests, and verification

Chris Huber remains responsible for every line of the change.