Expose runtime cache CLI commands

Summary

• Add fabrik cache blob put/get for direct content-addressed blob reads and writes from files, stdin, stdout, or output paths.
• Add fabrik cache action get/put/forget for inspecting, seeding, and deleting cached action results by digest.
• Extend command surface coverage and add shellspec coverage for direct cache workflows.
• Remove custom domain route configuration and route-related comments from Wrangler configs.

Testing

• mise exec -- cargo fmt --all -- --check
• mise exec -- cargo test -p fabrik-cli
• mise exec -- cargo clippy -p fabrik-cli --all-targets -- -D warnings
• mise exec -- cargo build --release
• mise exec -- shellspec spec/cache_runtime_spec.sh

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