fix(v0.6): reinstall corrected SQLite W41 conflict guard

[ammarheidari]

Authority

W41 remediation under #150 / tracker #146 after PR #153 merged to protected main at fb2cf62cb54c85d10a6ce71c048d37c54b8c68ba.

Problem

PR #153 corrected SQLite terminal .../partition/{n} parsing, but the durable SQLite guard marker remained legacy-topic-guard-scope = 2. A database that had already installed the older v2 trigger set could therefore be treated as current on restart and retain the stale first-/partition/ parsing logic.

A second rolling-upgrade risk also exists unless guarded at the database boundary: a late/restarted v2 process can replay its old installer after v3 activation and attempt to replace the corrected business triggers and move the marker back to v2.

Fix

• advance the SQLite conflict-guard schema marker from v2 to v3, forcing a transactional reinstall of corrected terminal-suffix triggers for existing v2 databases;
• install and retain a database-level monotonic anti-downgrade trigger on the guard schema marker so a late v2 installer aborts when attempting v3→v2;
• keep that monotonic fence present during current repair transactions and create it idempotently, so a missing business trigger can be repaired without opening a downgrade window;
• regression-test the exact pre-fix v2 SQLite installer SQL from commit 225eb37fd2;
• prove: stale v2 admits the problematic cluster-id-with-/partition/ claim; current startup upgrades v2→v3 and blocks it; a subsequent real v2 installer aborts and rolls back its stale trigger DDL; a current repair with the monotonic fence already present restores a missing business trigger and remains blocking.

PostgreSQL behavior is unchanged; its helper is versioned independently and was not affected by the SQLite parsing defect.

Scope

Two files only:

• src/backend/Infrastructure/Kafdeck.Infrastructure.Persistence/MutationConflictGuardSchema.cs
• tests/Kafdeck.Architecture.Tests/V06W41FleetPersistenceTests.cs

No new mutation kind, route, provider surface, generic executor, migration runner, release/version/manifest change, or publication action.

Admission

MERGE BLOCKED until all applicable exact-head CI is green, substantive review is complete, zero required unresolved threads remain, fresh current-head CODEOWNER approval from akhiabanchian exists, and final live head/base/main/mergeability/ruleset reconciliation passes.

Refs #150 #146.

[ammarheidari]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-24T18:00:45.341470Z	06d0c1f	Manual request

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[ammarheidari]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 78a53f7cba

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[ammarheidari]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

Reviewed commit: 06d0c1fee5

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".