fix(review): add SQLite migrateColumns entry for default_branch + fix WorkspaceSyncResult mock shape

Fixes two code review issues from PR #1274:
- H-1: Add ALTER TABLE migration for default_branch column in remote_agent_codebases so existing SQLite users get the column without data loss (NULL means syncWorkspace auto-detects the branch)
- M-1: Fix WorkspaceSyncResult mock in orchestrator.test.ts to return the correct shape matching the interface (branch/synced/previousHead/newHead/updated) and import BranchName for proper type casting

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core/src/db/adapters/sqlite.ts

@@ -215,6 +215,20 @@ export class SqliteAdapter implements IDatabase {
     } catch (e: unknown) {
       getLog().warn({ err: e as Error }, 'db.sqlite_migration_session_columns_failed');
     }
+
+    // Codebases columns
+    try {
+      const codebaseCols = this.db.prepare("PRAGMA table_info('remote_agent_codebases')").all() as {
+        name: string;
+      }[];
+      const codebaseColNames = new Set(codebaseCols.map(c => c.name));
+
+      if (!codebaseColNames.has('default_branch')) {
+        this.db.run('ALTER TABLE remote_agent_codebases ADD COLUMN default_branch TEXT');
+      }
+    } catch (e: unknown) {
+      getLog().warn({ err: e as Error }, 'db.sqlite_migration_codebases_columns_failed');
+    }
   }
 
   /**

packages/core/src/orchestrator/orchestrator.test.ts

@@ -5,6 +5,7 @@ import { makeTestWorkflow, makeTestWorkflowList } from '@archon/workflows/test-u
 import type { Conversation, Codebase, Session } from '../types';
 import { ConversationNotFoundError } from '../types';
 import type { WorkflowDefinition } from '@archon/workflows/schemas/workflow';
+import type { BranchName } from '@archon/git';
 
 // ─── Mock setup (BEFORE importing module under test) ─────────────────────────
 
@@ -127,7 +128,15 @@ mock.module('../utils/worktree-sync', () => ({
 }));
 
 // Git workspace sync mock
-const mockSyncWorkspace = mock(() => Promise.resolve({ fetched: true, reset: false }));
+const mockSyncWorkspace = mock(() =>
+  Promise.resolve({
+    branch: 'main' as BranchName,
+    synced: true,
+    previousHead: 'abc12345',
+    newHead: 'abc12345',
+    updated: false,
+  })
+);
 const mockToRepoPath = mock((p: string) => p);
 const mockToBranchName = mock((b: string) => b);