fix: skip cached state override when plug/humidifier ignore command

[bluetoothbot]

What

Gate _override_state on the result of _check_command_result in SwitchbotPlugMini.turn_on/turn_off and SwitchbotHumidifier._async_set_state/_set_level. Same shape as #502 (bot), extended to the other two device classes where the existing _check_command_result call was discarded.

Why

Audit follow-up to #502 (which fixed the bot half of #213). The same anti-pattern lives in plug.py and humidifier.py:

ret = self._check_command_result(result, 1, {0x80})  # protocol says "accepted?"
self._override_state({"isOn": True})                  # …but we override anyway

If the device returns anything other than the expected ACK byte, ret is False but the cached state still gets flipped, so the library lies about state to its caller. The bot version was observed in the wild (#213); the plug/humidifier versions are the same code shape and the existing _check_command_result calls show the original author already intended to validate — the gate was simply missing.

How

Two-line gate in each method, matching #502:

ret = self._check_command_result(result, ...)
if ret:
    self._override_state({...})
    self._fire_callbacks()
return ret

Behaviour for the accepted path is unchanged.

Testing

• New tests/test_plug.py (4 tests): accepted/rejected × turn_on/turn_off.
• New tests/test_humidifier.py (6 tests): accepted/rejected × turn_on/turn_off/set_level. Neither device had a test module before.
• Full suite: 1223 passed.

🤖 Generated with Claude Code

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Quality Report

Changes: 4 files changed, 201 insertions(+), 8 deletions(-)

Code scan: clean

Tests: passed (1223 passed)

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
switchbot/devices/humidifier.py	89.65% <100.00%> (+46.79%)	⬆️
switchbot/devices/plug.py	92.30% <100.00%> (+46.47%)	⬆️

... and 1 file with indirect coverage changes

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