fix: typing for message_handler

[Lash-L]

Same typing fix so that mypy passes for HA

Summary by CodeRabbit

• Bug Fixes

  • Improved compatibility for MQTT message handlers that may return an event object or no result.
  • Preserved existing message handling behavior while broadening supported handler annotations.

• Tests

  • Added coverage to confirm message handlers returning an optional event type are handled correctly.

[coderabbitai]

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Free

Run ID: b239462b-e57a-40fe-8379-a7c06a25d296

📥 Commits

Reviewing files that changed from the base of the PR and between cd50a98 and f8e81ae.

📒 Files selected for processing (2)

• harbor/mqtt.py
• tests/test_mqtt.py

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📝 Walkthrough

Walkthrough

The change updates type hints in harbor/mqtt.py to allow the message_handler callback to return HarborEvent | None instead of None, using postponed annotation evaluation and a TYPE_CHECKING import. A corresponding test is added to verify compatibility.

Changes

MQTT Message Handler Type Update

Layer / File(s)	Summary
Widen message_handler return type harbor/mqtt.py	Adds from __future__ import annotations, a TYPE_CHECKING-guarded import of HarborEvent, and updates the constructor's message_handler parameter type from Awaitable[None] to Awaitable[HarborEvent | None].
Test for widened return type tests/test_mqtt.py	Imports HarborEvent and adds test_message_handler_may_return_event, confirming _handle_message works with a handler annotated to return HarborEvent | None.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Poem

A type hint hops, both light and free,
HarborEvent joins the None, you see!
No runtime change, just clearer signs,
Tests confirm the handler's fine.
Thump-thump goes this rabbit's heart with glee! 🐇✨

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