Remove unused tempfile and libc dependencies

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What

Fixes the failing Rust static analysis — Detect unused dependencies CI job (cargo machete --with-metadata), which flagged two unused dependencies:

• garyx-agent-loop: tempfile (dev-dependency)
• garyx-bridge: libc

Verification

Confirmed both are genuinely unused, not false positives:

• tempfile (garyx-agent-loop): No references to tempfile/TempDir/tempdir/NamedTempFile in any source or test file. The actual tempfile::tempdir() usages live in garyx-bridge (correctly not flagged).
• libc (garyx-bridge): No libc token anywhere in the crate. The #[cfg(unix)] blocks use std (std::os::unix::fs::PermissionsExt), not libc. No build.rs exists.
• cargo check --all-features --all-targets passes for both crates, covering all feature-gated and test code paths.