feat: connect UI to situation graph start flow

docs/v0.4-route-status.md

@@ -5,10 +5,9 @@
   - Covered by `tests/app/api/cases-start-route.test.js`.
 
 - `app/api/start-case/route.js`
-  - Untracked earlier experiment / duplicate start route.
-  - Not referenced by the current UI.
-  - Still mentioned in untracked handoff docs.
-  - Leave untracked for now; recommend deletion once route migration is explicitly confirmed.
+  - Earlier experiment / duplicate start route.
+  - No repository UI/test references were found.
+  - Deleted from the working tree during UI connection cleanup.
 
 - `app/api/update-case/route.js`
   - Untracked future `updateCase` work.
@@ -16,5 +15,6 @@
   - Leave untracked for the current milestone.
 
 - Current UI status
-  - `components/scenario-form.jsx` still calls `/api/analyse`.
-  - No active UI path currently calls `/api/cases/start`, `/api/start-case`, or `/api/update-case`.
+  - `components/scenario-form.jsx` now calls `/api/cases/start` for the main experimental flow.
+  - `/api/analyse` remains available for compatibility.
+  - No active UI path currently calls `/api/update-case`.