test: pin mdns_timeout seconds-to-milliseconds conversion

[aiolibsbot]

What

Add regression tests that assert the timeout value AsyncMDNSResolver forwards to zeroconf's async_request.

Why

The public mdns_timeout argument is documented in seconds, but zeroconf's async_request expects milliseconds, so _resolve_mdns multiplies by 1000. Every existing test stubs async_request with return_value=True regardless of its arguments, so the conversion itself was never asserted. Dropping the * 1000 would silently turn a 5-second timeout into 5 milliseconds — breaking real on-network mDNS resolution — while the entire suite stayed green.

How

• New self-contained file tests/test_mdns_timeout_conversion.py (kept separate to avoid conflicting with the in-flight test_impl.py PRs).
• Patches load_from_cache to force the network path, captures async_request.call_args, and asserts the forwarded timeout is mdns_timeout * 1000 (2.5s → 2500.0; default 5.0s → 5000.0).
• Also asserts the query is issued through the resolver's own zeroconf instance.

Testing

ruff check and ruff format --check pass. pytest cannot run in this environment (no zeroconf/aiohttp installed); correctness is validated by the CI matrix.

---

Quality Report

Changes: 2 files changed, 106 insertions(+)

Code scan: clean

Tests: failed (FAILED)

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (5a01499) to head (e7ec65e).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #101   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         7    +1     
  Lines          521       564   +43     
  Branches        23        24    +1     
=========================================
+ Hits           521       564   +43     

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