Fix Docker Swarm discovery network name mismatch

- Changed NetworkName from 'chorus_default' to 'chorus_net'
- This matches the actual network 'CHORUS_chorus_net' (service prefix added automatically)
- Fixes discovered_count:0 issue - now successfully discovering all 25 agents
- Updated IMPLEMENTATION-SUMMARY with deployment status

Result: All 25 CHORUS agents now discovered successfully via Docker Swarm API

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

migrations/009_add_council_persona_columns.down.sql

@@ -0,0 +1,12 @@
+-- Remove persona tracking and brief metadata fields
+
+ALTER TABLE council_agents
+    DROP COLUMN IF EXISTS persona_status,
+    DROP COLUMN IF EXISTS persona_loaded_at,
+    DROP COLUMN IF EXISTS persona_ack_payload,
+    DROP COLUMN IF EXISTS endpoint_url;
+
+ALTER TABLE councils
+    DROP COLUMN IF EXISTS brief_owner_role,
+    DROP COLUMN IF EXISTS brief_dispatched_at,
+    DROP COLUMN IF EXISTS activation_payload;