fix: sync registry_generator.py with async event handler changes

[yie1d]

• This fixes the generator to match the changes made in commit 4fed163, which added async event handler support to cdp/registry.py but didn't update the generator. Without this fix, regenerating the code would revert the async handler changes and cause runtime errors.

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Summary by cubic

Updates registry_generator.py to generate an async handle_event that matches the async handler support in cdp/registry.py, preventing regenerated code from breaking at runtime.

• Bug Fixes
  • Make handle_event async and await coroutine handlers; call sync handlers directly.
  • Detect async handlers with inspect.iscoroutinefunction to preserve correct behavior during code generation.

^{Written for commit 9a1c62d. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

[yie1d]

fix #10