feat(KB-199): add retry CLI command and extension tool

- Add kb task retry command to CLI with --force and --all flags
- Implement runTaskRetry() to re-run failed or completed tasks
- Add kb_task_retry extension tool for Pi agent integration
- Update CLI help text and command registration
- Add comprehensive tests for retry command and extension tool
- Include changeset for patch release

packages/cli/src/__tests__/extension.test.ts

@@ -80,6 +80,7 @@ describe("kb pi extension", () => {
         "kb_task_attach",
         "kb_task_pause",
         "kb_task_unpause",
+        "kb_task_retry",
         "kb_task_duplicate",
         "kb_task_refine",
         "kb_task_import_github",