Add TMPDIR to PTY spawn modes

[sairus2k]

Closes #1213

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[greptile-apps]

Greptile Summary

Added TMPDIR environment variable to PTY spawn modes to support Nix development environments. The change follows the existing pattern for conditional environment variable passthrough (same as LANG, SSH_AUTH_SOCK).

• Applied consistently across all three PTY spawn functions: startSshPty(), startDirectPty(), and startPty()
• Uses the same conditional spread syntax to only include TMPDIR if it exists in the parent process
• Essential for Nix environments where TMPDIR is used for temporary directories (as seen in flake.nix)

Confidence Score: 5/5

• This PR is safe to merge with no risk
• The change is minimal (3 identical lines), follows established patterns exactly, and only adds conditional environment variable passthrough. No logic changes or side effects.
• No files require special attention

Important Files Changed

Filename	Overview
src/main/services/ptyManager.ts	Added TMPDIR environment variable passthrough to all three PTY spawn modes (startSshPty, startDirectPty, startPty) following the existing pattern for optional environment variables

_{Last reviewed commit: 2863587}

[arnestrickmann]

Thanks for flagging and for opening the PR!

[arnestrickmann]

could you resolve the merge conflicts?
would be amazing, thanks.