Require event hints for remote protocol errors

[Mirochill]

Summary

• make RemoteProtocolError.event_hint a required constructor argument
• update the public documentation to match the guarantee already provided by all internal call sites

Why

Issue #178 notes that every wsproto call site already supplies an event_hint, while the public signature still allows callers to construct a RemoteProtocolError without one. Requiring the argument makes the API describe the behavior the implementation already depends on and gives consumers a stable hint to react to.

This is intentionally an API-breaking change, matching the maintainer note that the issue is a candidate for a future minor API-breaking release.

Validation

• No local validation run, per this workspace's coordination-only policy.
• Verified statically that all in-repo RemoteProtocolError(...) call sites already provide event_hint=.
• Relying on the repository's remote CI for execution feedback.

[Kriechi]

Please add a changelog entry to document the API breaking change as minor. Also add the corresponding source-code comment annotation.

[Kriechi]

I was thinking about https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-versionchanged

example:

    .. versionchanged:: 2.3.0
       Changed the type of ``headers`` to :class:`HeaderTuple
       <hpack:hpack.HeaderTuple>`. This has no effect on current users.

[Mirochill]

Thanks, this is addressed in the follow-up commits: b1dc8d5 adds the 1.4.0 changelog entry, and f40f1b3 replaces the source note with a .. versionchanged:: 1.4.0 directive on RemoteProtocolError.

Remote checks now show the published tox jobs and codecov/patch green; codecov/project is still red, which looks like project coverage rather than this patch. No local tests were run, per my coordination-workspace policy.