docs(plan): record planning artifacts for recent work streams

Add task_plan/findings/progress notes for knowledge fact fidelity,
brand description context, media supply favorites, and the workspace
sync-to-39 deployment.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

task_plan.media-supply-favorites.md

@@ -0,0 +1,26 @@
+# Media Supply Favorites
+
+## Goal
+
+Persist favorites in PostgreSQL with multi-group membership, silent delisting cleanup,
+group-scoped removal, and server-side favorite search/pagination at 10 resources per page.
+
+## Phases
+
+- [x] Regression tests for multi-group membership and paginated lookup
+- [x] Database/store/service implementation
+- [x] HTTP routes and Swagger descriptions
+- [x] Favorites page search, pagination, and scoped removal
+- [ ] Go, frontend, migration, and browser verification
+
+## Non-negotiable Decisions
+
+- A resource may belong to multiple groups.
+- `(tenant_id, user_id, group_key, resource_id)` is the membership identity.
+- The 500-resource limit counts distinct resources, not memberships.
+- Favorites-page removal is group-scoped; resources-page removal is global.
+- Favorite resource details are queried server-side, 10 per page.
+
+## Errors Encountered
+
+None.