Guard genlocke data integrity edge cases

Block deletion of runs linked to a genlocke leg, prevent reactivating
completed/failed genlocke-linked runs, and guard encounter deletion
against genlocke transfer references with clear 400 errors.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.beans/nuzlocke-tracker-pm9f--genlocke-edge-cases.md

@@ -1,17 +1,33 @@
 ---
 # nuzlocke-tracker-pm9f
 title: Genlocke edge cases
-status: draft
+status: in-progress
 type: task
+priority: normal
 created_at: 2026-02-09T08:48:46Z
-updated_at: 2026-02-09T08:48:46Z
+updated_at: 2026-02-09T11:03:35Z
 parent: nuzlocke-tracker-25mh
 ---
 
-Collect and evaluate edge cases for genlocke tracking. Review periodically to decide if any need dedicated handling.
+Guard genlocke-related data integrity edge cases. Audited existing endpoints for gaps in validation when runs, encounters, or legs interact with genlocke tracking.
 
-## Edge Cases
+## Checklist
 
-- [ ] Prevent run deletion if the run is linked to a genlocke leg. The `DELETE /runs/{id}` endpoint should check for a `GenlockeLeg` with matching `run_id` and return 400 if found, telling the user to remove the run from the genlocke first.
-- [ ] What happens if a user tries to advance a leg twice? (Currently guarded by "next leg already has a run" check)
-- [ ] What if the user edits a completed run back to active after the genlocke has already been marked completed/failed?
+### Critical
+
+- [x] **Block deletion of genlocke-linked runs.** `DELETE /runs/{id}` now returns 400 if the run belongs to a genlocke leg. (`runs.py`)
+
+- [x] **Block reactivation of completed/failed genlocke-linked runs.** `PATCH /runs/{id}` now returns 400 when trying to set status back to `active` on a genlocke-linked run. (`runs.py`)
+
+### High
+
+- [x] **Guard encounter deletion against transfer references.** `DELETE /encounters/{id}` now checks for GenlockeTransfer references and returns 400 instead of a raw FK constraint violation. (`encounters.py`)
+
+### Already handled (verified during audit)
+
+- [x] Advance leg twice — guarded by "next leg already has a run" check in `advance_leg`
+- [x] Transfer eggs blocking starter route — transfer-target encounters are excluded from route-lock checks (`encounters.py:90-96`)
+- [x] Shiny flag preservation during transfers — `is_shiny` is copied to egg encounter (`genlockes.py`)
+- [x] Genlocke deletion cascading properly — CASCADE on FK for both `GenlockeLeg` and `GenlockeTransfer`, runs properly unlinked
+- [x] Duplicate source transfers — prevented in practice by the "next leg already has a run" guard; `target_encounter_id` has a UNIQUE constraint
+- [x] Empty transfer list — valid behavior, advances leg without transfers