fix: pass through cargo install --path

[piorpua]

Summary

• Treat cargo install --path <dir> as a native cargo install, not a vx global package install
• Add a regression case so local path installs are not routed through the global package bridge

Test Plan

• vx cargo test -p vx-cli --test npm_global_bridge_tests
• vx cargo fmt --all -- --check
• vx git diff --check

[piorpua]

Updated after review:

• Handles both --path <dir> and --path=<dir> forms.
• Also skips the global-package bridge for Cargo external/non-default sources: --git, --registry, and --index, including --flag=value variants.
• Added regression cases for those forms, including --path <dir> --verbose.

Verification:

• vx cargo test -p vx-cli --test npm_global_bridge_tests (34 passed)
• vx cargo fmt --all -- --check
• vx git diff --check