fix: clean up pending permissions when session is deleted

[hendem]

Fixes #3013

Summary

• Add init(), dispose(), and clearSession() to PermissionNext namespace
• Subscribe to session.deleted bus event to clean up orphaned pending permissions
• Reject all pending permission requests when their session is deleted

Problem

When a session is deleted, any pending permission requests for that session remain in the pending map indefinitely. This causes:

• Memory accumulation over time as pending entries are never removed
• Orphaned promises that never resolve or reject

Solution

Subscribe to the session.deleted event and clean up all pending permissions for deleted sessions by:

1. Rejecting pending promises with RejectedError
2. Removing entries from the pending map

Testing

Added comprehensive tests in test/permission/cleanup.test.ts.