fix(knowledge): prevent KB deletion deadlocks

[icecrasher321]

Summary

• Use FOR NO KEY UPDATE in the shared knowledge base soft-delete transaction. This lets an in-flight embedding insert complete its foreign-key check and release its document lock before deletion archives the document, while still serializing competing KB writes.
• Add PostgreSQL regression coverage for concurrent publication and deletion, competing deletes, workspace scope, and search-index deletion guards.

Type of Change

• Bug fix

Testing

• Reproduced PostgreSQL 40P01 with the original lock; the regression passes with the fix.
• 8 PostgreSQL integration tests and 83 focused unit tests passed.
• App/auth type checks, repository lint, all 46 audits (including strict API boundary validation), block registry, docs manifest, and git diff --check passed.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Sep 8, 2026 11:46pm UTC

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the narrower lock preserves required write serialization while resolving the documented lock cycle.

Summary

• Changes the deletion lock from FOR UPDATE to FOR NO KEY UPDATE.
• Allows in-flight embedding publication to complete before child documents are archived.
• Adds PostgreSQL integration coverage for publication/deletion concurrency, competing deletes, workspace scoping, and search-index guards.

Diagram

sequenceDiagram
    participant P as Embedding publication
    participant D as Document row
    participant K as Knowledge-base row
    participant X as KB deletion

    P->>D: FOR UPDATE
    X->>K: FOR NO KEY UPDATE
    X->>D: Archive document (waits)
    P->>K: FK check (KEY SHARE, compatible)
    P->>P: Insert embedding
    P-->>D: Commit and release lock
    X->>D: Archive document
    X->>K: Soft-delete knowledge base
    X-->>X: Commit

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