Don't crash on startup when version cache dir is unwritable

[ikatyal2110]

When aider starts in an environment where Path.home() resolves to an unwritable path (e.g. / in certain containers or WSL configs), the mkdir and touch calls in the finally block of check_version() raise PermissionError, crashing startup before the user can do anything. The fix wraps those two lines in a try/except OSError so a bad home directory silently skips the cache write instead of aborting. Fixes #2865.

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✅ ikatyal2110
❌ ikatyal21
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[goransh-buh]

Nice, straightforward implementation.