PyodideBridge should clear initPromise on init failure to allow retry

[bbopen]

Problem

If loadPyodide or loadPackage fails during initialization, initPromise remains rejected and is never cleared. Subsequent calls return the same rejected promise, so the bridge cannot recover without creating a new instance.

Evidence

• src/runtime/pyodide.ts: ensureReady() returns initPromise when set; doInit() failures do not reset it.

Acceptance criteria

• On init failure, clear initPromise and py so a subsequent call can retry initialization.
• Add a test that simulates a loadPackage or loadPyodide failure, then fixes it and retries successfully.

[bbopen]

Resolved by PR #150. BoundedContext clears initPromise on init failure, allowing retry.