feat(migration): complete Step 1 of ActiveDid migration - update () to use new API

- Update () to call () with fallback to settings
- Maintain backward compatibility while using new active_identity table
- Update migration plan documentation to reflect completed Step 1
- Restore Playwright workers to 4 (was accidentally set to 1)

Tests: 39/40 passing (1 unrelated UI failure)
Migration progress: Step 1 complete, ready for Step 2 dual-write implementation

src/utils/PlatformServiceMixin.ts

@@ -836,8 +836,10 @@ export const PlatformServiceMixin = {
           return defaults;
         }
 
-        // Determine which DID to use
-        const targetDid = did || defaultSettings.activeDid;
+        // Determine which DID to use - try new active_identity table first, fallback to settings
+        const activeIdentity = await this.$getActiveIdentity();
+        const targetDid =
+          did || activeIdentity.activeDid || defaultSettings.activeDid;
 
         // If no target DID, return default settings
         if (!targetDid) {