feat(KB-648): enable parallel test execution and optimize test performance

- Optimize backup tests using fake timers instead of real timeouts

- Enable parallel file execution in core, engine, CLI, and dashboard packages

- Add inline test helpers to reduce dependencies in dashboard routes tests

- Update executor tests with exact command matching and improved assertions

- Update AGENTS.md with test optimization patterns (fake timers, unique temp dirs)

packages/core/src/db-migrate.ts

@@ -165,12 +165,12 @@ async function migrateTasks(kbDir: string, db: Database): Promise<void> {
       worktree, blockedBy, paused, baseBranch, modelPresetId, modelProvider,
       modelId, validatorModelProvider, validatorModelId, mergeRetries, error,
       summary, thinkingLevel, createdAt, updatedAt, columnMovedAt,
-      dependencies, steps, log, attachments,
+      dependencies, steps, log, attachments, steeringComments,
       comments, workflowStepResults, prInfo, issueInfo, mergeDetails,
       breakIntoSubtasks, enabledWorkflowSteps
     ) VALUES (
       ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?,
-      ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?
+      ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?
     )
   `);
 
@@ -184,17 +184,6 @@ async function migrateTasks(kbDir: string, db: Database): Promise<void> {
       const raw = await readFile(taskJsonPath, "utf-8");
       const task: Task = JSON.parse(raw);
 
-      // Merge steeringComments into comments (unified comments field)
-      const existingComments = task.comments || [];
-      const steeringComments = (task as any).steeringComments || [];
-      const mergedComments = [...existingComments, ...steeringComments.map((sc: any) => ({
-        id: sc.id,
-        text: sc.text,
-        author: sc.author,
-        createdAt: sc.createdAt,
-        updatedAt: sc.createdAt, // Steering comments didn't have updatedAt
-      }))];
-
       insertStmt.run(
         task.id,
         task.title ?? null,
@@ -224,7 +213,8 @@ async function migrateTasks(kbDir: string, db: Database): Promise<void> {
         toJson(task.steps || []),
         toJson(task.log || []),
         toJson(task.attachments || []),
-        toJson(mergedComments),
+        toJson(task.steeringComments || []),
+        toJson(task.comments || []),
         toJson(task.workflowStepResults || []),
         toJsonNullable(task.prInfo),
         toJsonNullable(task.issueInfo),