feat: add testdrive-jsui as git submodule

Set up testdrive-jsui as a git submodule pointing to separate repository.
This enables independent development and versioning of the testdrive-jsui capability.

The submodule will need manual synchronization of recent refactoring changes:
- Consolidated asset structure (js/, static/)
- Plugin self-declaration methods
- Updated README with standalone usage docs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.gitmodules

@@ -8,3 +8,6 @@
 [submodule "capabilities/kaizen-agentic"]
 	path = capabilities/kaizen-agentic
 	url = http://92.205.130.254:32166/coulomb/kaizen-agentic.git
+[submodule "capabilities/testdrive-jsui"]
+	path = capabilities/testdrive-jsui
+	url = http://92.205.130.254:32166/coulomb/testdrive-jsui.git