[bug] quest post: ID allocation race under concurrent writers

[kunallanjewar]

Summary

Concurrent quest.Post calls within the same project can surface duplicate-ID or primary-key conflicts to callers. The current allocation path doesn't guarantee uniqueness under contention from multiple writers (e.g. parallel agents or scripts hitting the same project).

Affected files

• internal/quest/post.go
• internal/quest/post_test.go

Acceptance

• Concurrent quest.Post calls in the same project succeed without surfacing duplicate-ID or PK conflicts.
• Allocated quest IDs remain unique and monotonic within a project under concurrent posting.
• Add regression coverage with multiple concurrent posters under the current SQLite WAL setup.
• Code comments accurately describe the concurrency guarantee the implementation provides.