docs(dsql): update SELECT FOR UPDATE guidance and evals

[mchenjh]

Related

Part of a coordinated Aurora DSQL SELECT FOR UPDATE rollout. Sibling PR links will be added after all PRs are opened.

Changes

• Remove the obsolete all-primary-key equality and single-table restrictions from DSQL guidance.
• Document commit-time OCC behavior, supported lock clauses, SQLSTATE 40001 retries, and 10 MiB locked-primary-key accounting.
• Correct framework-specific guidance, including Rails transaction locking.
• Add a joined/non-key SELECT FOR UPDATE functional eval and precise row-modification matcher coverage.
• Bump the databases-on-aws plugin version to 1.9.0.

Validation: 60 deterministic eval-runner tests passed; canonical guidance matches the MCP steering mirror; 22 eval prompts contain 93 assertions. A full model eval run was attempted, but the subject runner timed out after 180 seconds with zero turns on the first eval, so no model-quality result was produced.

Acknowledgment

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the project license.

Related rollout PRs

• Canonical agent guidance: docs(dsql): update SELECT FOR UPDATE guidance and evals #271
• Kiro Power mirror: docs(aurora-dsql): update SELECT FOR UPDATE Kiro guidance mcp#4607
• Flyway compatibility cleanup: Remove obsolete Aurora DSQL table-lock override flyway/flyway-community-db-support#149
• ORM adapters: Update Hibernate and Tortoise SELECT FOR UPDATE support aurora-dsql-orms#626
• Samples: Refresh Aurora DSQL SELECT FOR UPDATE sample guidance aws-samples/aurora-dsql-samples#1821

[mchenjh]

Review pass 1

Reviewed the rollout diff finalized in commit e453c9b with 16+ independent review roles covering correctness, framework behavior, documentation, security, tests, and scope. Findings addressed included Rails transaction boundaries, Hibernate inner-join wording, Tortoise outer-join behavior, supported lock-clause guidance, SQLSTATE 40001 retry scope, and 10 MiB locked-primary-key accounting. The Flyway change was intentionally kept as compatibility cleanup; migration-wide coordination remains out of scope.

Validation after fixes: deterministic eval-runner tests passed and the canonical guidance matched the MCP mirror.

[mchenjh]

Review pass 2

A fresh 16-reviewer convergence pass was run against the post-fix rollout, followed by direct current-file verification of every reported issue. No unresolved behavioral or CI-blocking findings remain in commit e453c9b.

Final validation: 60 deterministic eval-runner tests passed; 22 prompts / 93 assertions validate; canonical and MCP steering files are byte-identical; all five diffs pass git diff --check. A full 22-prompt model eval was attempted, but the subject runner timed out after 180 seconds with zero turns on eval 1, so no model-quality result was produced.

[anwesham-lab]

LGTM, ran new fleet of reviewers and found no blocking issues or risks. Language audit was clean. Was able to reproduce evals!