fix(pl18): prevent hang when pressing power button during USB charging

[richardclli]

Fixed by opencode + deepseek with prompt:

Try to explore the code and figure out how to fix the problem:

1. Start investigating in @radio/src/targets/pl18/board.cpp
2. PL18U radio has this problem
3. When plugin USB the radio will automatic power up and run board.cpp and enter battery charging loop
4. if we presses the power on button before or during battery charging (not sure the exact timing) the radio will hangs
5. Battery charging will have animation using w2812 LEDs, and pressing power button will make the animation stops and hangs

It found the problem and fixed it automatically ^.^

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a null-pointer safety check in battery_charge_end() to prevent unconditional cleanup of a potentially null window, and introduces a 10ms delay in the boardInit() power-on timing loop. Both are platform-specific fixes to the PL18 target.

Changes

PL18 Platform Fixes

Layer / File(s)	Summary
Battery charge window cleanup safety radio/src/targets/pl18/battery_driver.cpp	battery_charge_end() now conditionally clears and deletes the chargeWindow LVGL object only when it is non-null, preventing unsafe cleanup when the pointer is already null.
Power-on loop timing adjustment radio/src/targets/pl18/board.cpp	A 10ms delay is added to the charger/power-on wait loop in boardInit() to adjust timing behavior during board initialization.

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🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Description check	⚠️ Warning	PR description lacks standard template structure with issue reference and formal summary section.	Add 'Fixes #XXXX' reference at the top and restructure as formal summary. Replace informal generation notes with clear technical description of the changes.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the primary fix: preventing a hang when the power button is pressed during USB charging, which aligns with both code changes.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch richardclli/fix-pl18u-hangs-presspwr-wusb

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[richardclli]

@pfeerick I have tested this as well. No more hangs.