Every Rust workspace passes fmt, clippy and tests on its target platforms #318

Part of #311 (Group D, CI coverage). Owner: not assigned. Task base and PR target: develop. Start after #317 merges (same file). Coordinate with #194 Part 2, which deletes low-value tests.

Intended behavior

CI checks every Rust workspace in the repository on the platforms where its code runs: format, clippy with -D warnings, and tests.

Current behavior

• cargo fmt --check runs only for the elastos workspace (ci.yml:56-58). test-capsules runs clippy and tests for capsules/* (ci.yml:312-318), but no format check.
• The nine elastos/tools/* workspaces are never clippy-checked or tested in CI:
  • browser-engine-supervisor, browser-local-exit, browser-native-proxy-engine, browser-playwright-engine, browser-stream-bridge;
  • browser-vm-guest-control-bridge, browser-vm-runtime-relay, componentize, vsock-proxy.
• test-elastos builds two of them (ci.yml:257-258). justfile:195-199 covers only browser-local-exit, and only in just verify.
• No CI job runs clippy or cargo test on macOS. Code behind cfg(target_os = "macos"), for example in the elastos-vz crate, is compiled by the source-home build but never linted or tested.

Implementation notes

• Format: loop over every Cargo.toml workspace root in the existing lint job; this is cheap.
• Tools: add a test-tools job, or extend test-capsules to elastos/tools/*. It shares target-build through .cargo/config.toml.
• macOS: add clippy and tests for the crates that contain macOS-only code to the macOS job, or to a new macOS job. Keep the cost low with the compiler cache (CI speed: make the compiler cache store entries and shorten the macOS path #310, item 1).

Done means

• Every workspace passes cargo fmt --check. Test: a deliberate format error in a capsule fails CI (one test PR).
• Every elastos/tools/* workspace passes clippy with -D warnings and its tests in CI. Proof: the job log.
• macOS-only code passes clippy and its tests on a macOS runner. Proof: the job log.