Adds the data layer for per-item agent prompts. Markdown frontmatter
gets an `agent_prompt:` block scalar that survives the importer
round-trip (newlines preserved), and `resolveWorkflowPrompt()` walks
task → epic → plan → built-in default returning both the resolved
string and the source level. Walk is slug-based, not parent_id-based,
because the importer leaves parent_id briefly null mid-transaction.
tRPC `backlog.getWorkflowPrompt` returns ownOverride + effectivePrompt
so future UI can render the override box + preview without two
queries. `backlog.updateWorkflowPrompt` is owner/admin-gated (prompts
change downstream Cursor/Claude behavior) and audit-logged on every
write.
UI deferred — apps/web doesn't have a backlog-item detail panel yet;
the existing object-detail panel is for the objects table. Follow-up
filed at Task-workflow-prompt-task-detail-ui.md.
Co-authored-by: Cursor <cursoragent@cursor.com>
72aa2a5f0c