2026.7.20-canary.1002

feat(server): impl doc gc (#15282)

#### PR Dependency Tree


* **PR #15282** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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## Summary by CodeRabbit

* **New Features**
* Added automated document cleanup to reconcile missing workspace docs,
delete related stored data, and recover if the doc returns.
* Added effect-based follow-up reconciliation for search indexing,
Copilot embeddings, and comment attachment cleanup with explicit
acknowledgements.
* **Bug Fixes**
* Deleted-document references now persist as dangling references rather
than disappearing.
* Improved document deletion flow to enforce permissions and ensure
authorized deletions succeed.
* **Tests**
* Expanded coverage for cleanup recovery, indexing/embedding
reconciliation, permissions, and reference semantics.
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