fix(a2a): add cross-platform atomic write safety & handle Windows chm…

[Adityakk9031]

Fixes #84

Summary

Fixes an issue in a2a_context.py where _atomic_write raised unhandled OSError / PermissionError on Windows environments during chmod(0o600) calls, and left temporary .tmp context files dangling when atomic writes were interrupted.

Problem

1. Windows Compatibility: POSIX file permissions (chmod(0o600)) throw OSError / PermissionError on Windows or non-POSIX file systems.
2. Leftover Temp Files: If _atomic_write failed prior to os.replace, the .tmp file was left in the state directory, causing subsequent os.replace calls to fail with PermissionError or file lock conflicts.

Fix Applied

• Cross-Platform Safety: Wrapped POSIX chmod(0o600) calls in contextlib.suppress(OSError) so file creation succeeds across Windows and non-POSIX environments.
• Guaranteed Cleanup: Added a finally block in _atomic_write to safely unlink any leftover .tmp file on failure.
• Explicit Encoding: Specified encoding="utf-8" when writing JSON context files.

Verification

• Executed unit test suite for A2A context management:

  python -m pytest tests/test_a2a.py

[Adityakk9031]

@dimavrem22 and @alex-w-99 have a look

[dimavrem22]

@dimavrem22 and @alex-w-99 have a look

thanks @Adityakk9031 to help us review the prs, can you please let us know the agent handle of the identity you're using. Thanks mate

[Adityakk9031]

@dimavrem22 Thanks I used OpenCode together with Codex as coding assistants for this PR. I reviewed and finalized the changes before submitting.

[dimavrem22]

@dimavrem22 Thanks I used OpenCode together with Codex as coding assistants for this PR. I reviewed and finalized the changes before submitting.

no i mean your inkbox agent handle

[Adityakk9031]

@dimavrem22 Ah got it, thanks for clarifying! My Inkbox agent handle is adityakk.

[dimavrem22]

@dimavrem22 Ah got it, thanks for clarifying! My Inkbox agent handle is adityakk.

nice! How'd you run into this issue out of curiosity? did you run A2A on a windows? Im thinking of ways to harden the code against issues like this in the future

[Adityakk9031]

Thanks @dimavrem22! Yes, exactly I was running the plugin and running test suites on a Windows machine.

On Windows/NTFS, POSIX chmod(0o600) calls raise PermissionError/OSError. Since there wasn't a finally block to clean up the .tmp file when chmod failed, subsequent os.replace attempts hit file lock conflicts.

Adding cross-platform CI matrix testing (windows-latest alongside Linux) in GitHub Actions would be a great way to catch OS-specific file system edge cases automatically!