Fix Nix cargo output hashes for rmcp and filedescriptor

[tyleranton]

Fixes #7759:

• Drop the stale rmcp entry from codex-rs/default.nix’s cargoLock.outputHashes since the crate now comes from crates.io and no longer needs a git hash.
• Add the missing hash for the filedescriptor-0.8.3 git dependency (from pakrym/wezterm) so buildRustPackage can vendor it.

[github-actions]

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[tyleranton]

I have read the CLA Document and I hereby sign the CLA

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Add output hash for portable-pty git dependency

The cargoLock.outputHashes list now includes the new git-sourced filedescriptor, but it still omits portable-pty even though Cargo.toml patches that crate to the same git repo/branch (line 292) and Cargo.lock records it as a git source (portable-pty 0.9.0 from pakrym/wezterm). When rustPlatform.buildRustPackage evaluates this Nix file it will continue to fail with a “missing output hash for portable-pty-0.9.0” error, so the Nix build remains broken after this change.

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[etraut-openai]

Thanks for the contribution!