Fix task resumption in the API module

[cte]

Important

Fixes task resumption in api.ts by handling webview launch status and updating sendMessage for headless mode.

• Behavior:
  • In api.ts, resumeTask() now waits for webview launch and logs if not launched, continuing in headless mode.
  • sendMessage() checks if webview is launched; if not, submits message directly to task channel.
• Utilities:
  • Adds waitForWebviewLaunch() in api.ts to wait for webview launch with a timeout.
• Tests:
  • Updates api-send-message.spec.ts to mock getCurrentTask and test sendMessage behavior with and without webview launch.

^{This description was created by for 9ac20a2. You can customize this summary. It will automatically update as commits are pushed.}

[roomote]

Rooviewer   See task

Re-reviewed after 9ac20a2. The test mock fix resolves the getCurrentTask breakage. One item remains open.

• getCurrentTask() called unconditionally in sendMessage breaks existing test mocks -- fixed by adding the mock to the provider object
• No test coverage for the new headless fallback paths in sendMessage or resumeTask

Previous reviews

• 30b4339: Review #1

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}