Migrate the Investigation page route to own durable investigation identity
via its route [id] segment, passing that ID through to ScenarioForm for
hydration and persistence.
- Remove hardcoded INVESTIGATION_ID constant from page.jsx
- Use params.id as routeId; loadInvestigation(routeId) loads by identity
- Pass investigationId prop into ScenarioForm in both branch paths
- Session restore calls loadInvestigation(investigationId)
- All 4 save call sites include id: investigationId in snapshot
- Missing identified Investigation starts clean (no singleton fallback)
- Legacy singleton is not migrated/fallback-loaded
- Portfolio remains unmigrated; Report remains unmigrated; Restart untouched
Deterministic tests: 34/34 pass (scenario-form-persistence + investigation-storage)
Build: PASS
Live Playwright: all criteria verified at /investigations/v060e-live
robbond