feat: Add VEX Status Chip component and integration tests for reachability drift detection

- Introduced `VexStatusChipComponent` to display VEX status with color coding and tooltips.
- Implemented integration tests for reachability drift detection, covering various scenarios including drift detection, determinism, and error handling.
- Enhanced `ScannerToSignalsReachabilityTests` with a null implementation of `ICallGraphSyncService` for better test isolation.
- Updated project references to include the new Reachability Drift library.

src/Excititor/__Libraries/StellaOps.Excititor.Storage.Postgres/Migrations/005b_migrate_timeline_events_data.sql

@@ -0,0 +1,147 @@
+-- Excititor Schema Migration 005b: Complete timeline_events Partition Migration
+-- Sprint: SPRINT_3422_0001_0001 - Time-Based Partitioning
+-- Task: 4.2 - Migrate data from existing table
+-- Category: C (data migration, requires maintenance window)
+--
+-- IMPORTANT: Run this during maintenance window AFTER 005_partition_timeline_events.sql
+-- Prerequisites:
+--   1. Stop application writes to vex.timeline_events
+--   2. Verify partitioned table exists: \d+ vex.timeline_events_partitioned
+--
+-- Execution time depends on data volume. For large tables (>1M rows), consider
+-- batched migration (see bottom of file).
+
+BEGIN;
+
+-- ============================================================================
+-- Step 1: Verify partitioned table exists
+-- ============================================================================
+
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_class c
+        JOIN pg_namespace n ON c.relnamespace = n.oid
+        WHERE n.nspname = 'vex' AND c.relname = 'timeline_events_partitioned'
+    ) THEN
+        RAISE EXCEPTION 'Partitioned table vex.timeline_events_partitioned does not exist. Run 005_partition_timeline_events.sql first.';
+    END IF;
+END
+$$;
+
+-- ============================================================================
+-- Step 2: Record row counts for verification
+-- ============================================================================
+
+DO $$
+DECLARE
+    v_source_count BIGINT;
+BEGIN
+    SELECT COUNT(*) INTO v_source_count FROM vex.timeline_events;
+    RAISE NOTICE 'Source table row count: %', v_source_count;
+END
+$$;
+
+-- ============================================================================
+-- Step 3: Migrate data from old table to partitioned table
+-- ============================================================================
+
+INSERT INTO vex.timeline_events_partitioned (
+    id, tenant_id, project_id, event_type, entity_type, entity_id,
+    actor, details, occurred_at
+)
+SELECT
+    id, tenant_id, project_id, event_type, entity_type, entity_id,
+    actor, details, occurred_at
+FROM vex.timeline_events
+ON CONFLICT DO NOTHING;
+
+-- ============================================================================
+-- Step 4: Verify row counts match
+-- ============================================================================
+
+DO $$
+DECLARE
+    v_source_count BIGINT;
+    v_target_count BIGINT;
+BEGIN
+    SELECT COUNT(*) INTO v_source_count FROM vex.timeline_events;
+    SELECT COUNT(*) INTO v_target_count FROM vex.timeline_events_partitioned;
+
+    IF v_source_count <> v_target_count THEN
+        RAISE WARNING 'Row count mismatch: source=% target=%. Check for conflicts.', v_source_count, v_target_count;
+    ELSE
+        RAISE NOTICE 'Row counts match: % rows migrated successfully', v_target_count;
+    END IF;
+END
+$$;
+
+-- ============================================================================
+-- Step 5: Swap tables
+-- ============================================================================
+
+-- Rename old table to backup
+ALTER TABLE vex.timeline_events RENAME TO timeline_events_old;
+
+-- Rename partitioned table to production name
+ALTER TABLE vex.timeline_events_partitioned RENAME TO timeline_events;
+
+-- ============================================================================
+-- Step 6: Enable RLS on new table (if applicable)
+-- ============================================================================
+
+ALTER TABLE vex.timeline_events ENABLE ROW LEVEL SECURITY;
+
+-- ============================================================================
+-- Step 7: Add comment about partitioning
+-- ============================================================================
+
+COMMENT ON TABLE vex.timeline_events IS
+    'VEX timeline events. Partitioned monthly by occurred_at. Migrated on ' || NOW()::TEXT;
+
+COMMIT;
+
+-- ============================================================================
+-- Post-migration verification (run manually)
+-- ============================================================================
+--
+-- Verify partition structure:
+--   SELECT tableoid::regclass, count(*) FROM vex.timeline_events GROUP BY 1;
+--
+-- Verify BRIN index is being used:
+--   EXPLAIN (ANALYZE, BUFFERS) SELECT * FROM vex.timeline_events
+--     WHERE occurred_at > NOW() - INTERVAL '1 day';
+--
+-- After verification, drop old table:
+--   DROP TABLE IF EXISTS vex.timeline_events_old;
+
+-- ============================================================================
+-- Batched migration alternative (for very large tables)
+-- ============================================================================
+--
+-- If the table is very large (>10M rows), use this batched approach instead:
+--
+-- DO $$
+-- DECLARE
+--     v_batch_size INT := 100000;
+--     v_offset INT := 0;
+--     v_inserted INT;
+-- BEGIN
+--     LOOP
+--         INSERT INTO vex.timeline_events_partitioned
+--         SELECT * FROM vex.timeline_events
+--         ORDER BY occurred_at
+--         LIMIT v_batch_size OFFSET v_offset;
+--
+--         GET DIAGNOSTICS v_inserted = ROW_COUNT;
+--         v_offset := v_offset + v_batch_size;
+--
+--         RAISE NOTICE 'Migrated % rows (offset: %)', v_inserted, v_offset;
+--
+--         EXIT WHEN v_inserted < v_batch_size;
+--
+--         -- Allow checkpoint between batches
+--         PERFORM pg_sleep(0.1);
+--     END LOOP;
+-- END
+-- $$;