Build the Rust workspace and Wasm artifacts

[keys-i]

Motivation

The existing package graph verifies source identities but ships metadata only. This change turns those boundaries into buildable Rust crates and checked-in WebAssembly outputs.

Closes #9

Changes

• replace the Node metadata workspace with four Rust crates: krad-clang, krad-musl, krad-libs, and krad-utils
• verify exact local Cheerp sources, revisions, licenses, and the pinned compiler archive SHA-256 without downloading inputs
• build no_std Rust Wasm libraries and compile a real C++ fixture through Cheerp
• check in the five generated .wasm/ES-module artifacts and document exact limits
• cover ABI helpers plus CLI help, invalid command, and missing-input failures

Verification

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace (7 tests)
• cargo run -p krad-utils -- build ../research dist
• Node: Cheerp krad_add(20, 22) == 42; Rust Wasm exports returned expected values
• file dist/*: four WebAssembly MVP modules
• two builds produced identical SHA-256 hashes

Risks

The build trusts only the exact pinned local source checkouts and SHA-verified Cheerp archive. It does not provide a complete libc/sysroot, in-browser compiler, Linux/BSD distribution, or measured advantage over Cheerp. The commit is unsigned at the user request because the configured SSH signing key was locked.

Rollback

Revert commit 46ebcb7af1384f03e720209d4ea064229c2849ec.