feat: align SDK with updated OpenAPI spec and add missing unit tests

- Update generated types from new openapi.yaml (capsule stats, usage,
  metrics, pause/resume lifecycle, host/channel management, auth flow)
- Add Capsule pause/resume/ping/getMetrics lifecycle methods
- Add Capsule.waitForReady abort signal support
- Add PtyManager.connect and PtySession disposal
- Fix HttpClient empty-body response handling (content-length: 0)
- Add streamProcess() to CommandManager for background process streams
- Add integration tests for capsule lifecycle, git, and PTY features
- Add unit tests for AsyncQueue error paths, PtySession.close,
  Git.checkout without create, Git.add single string,
  Notebook.execCell error case, and PtyStartOptions fields

Makefile

@@ -1,7 +1,7 @@
 # Makefile
 .PHONY: generate lint test test-integration check build
 
-SPEC_URL = "https://raw.githubusercontent.com/wrennhq/wrenn/refs/heads/main/internal/api/openapi.yaml"
+SPEC_URL = "https://git.omukk.dev/wrenn/wrenn/raw/branch/feat/migrate-to-ch/internal/api/openapi.yaml"
 SPEC_PATH = "api/openapi.yaml"
 
 generate: