Inspect and export normalized toolchain contracts

Fabrik now ships a fabrik toolchain inspect command that derives a normalized toolchain contract from your mise.toml. You can include optional mise.lock metadata and a stable blake3 fingerprint for caching and remote execution, and target a specific platform (for example linux-x64) with --platform to resolve platform-specific lockfile data. Build action PATH values are now built from explicit tool directories instead of inheriting the parent shell.