fix(main): use tempfile.mkstemp for collision-safe writable directory check

[Copilot]

_is_directory_writable used a fixed .write_test.tmp filename, causing potential collisions and flaky results when multiple processes/threads run the check concurrently in the same directory. Cleanup also only happened on the happy path.

Changes

• Unique temp file: replaced hardcoded path / ".write_test.tmp" with tempfile.mkstemp(dir=path), producing a distinct file per call
• Guaranteed cleanup: moved unlink + close into a finally block so the temp file is always removed, even if the write raises mid-way

# Before
test_file = path / ".write_test.tmp"
with open(test_file, "w", encoding="utf-8") as tmp:
    tmp.write("test")
test_file.unlink(missing_ok=True)

# After
fd, tmp_path = tempfile.mkstemp(dir=path)
try:
    os.write(fd, b"test")
    return True
finally:
    os.close(fd)
    Path(tmp_path).unlink(missing_ok=True)

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[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
11564	10528	91%	89%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
ardupilot_methodic_configurator/main.py	75%	🟢
TOTAL	75%	🟢

updated for commit: f5b8ec7 by action🐍