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

.changeset/add-retry-cli-command.md

@@ -0,0 +1,5 @@
+---
+"@dustinbyrne/kb": minor
+---
+
+Add `kb task retry <id>` CLI command to retry failed tasks from command line