feat(cli): type headless scratch scripts

[pgherveou]

Summary

• generate a standalone declaration for the truapi, host, and assert
  globals injected into headless host scripts
• copy the matching declaration beside each managed scratch script and reference
  it with a portable relative path
• ship and verify the declaration in source packages and prebuilt CLI archives

Verification

• cargo test -p truapi-host-cli
• make cli-runner
• cargo +nightly fmt --check --package truapi-host-cli
• cargo +nightly clippy -p truapi-host-cli --all-targets --all-features -- -D warnings
• regenerated truapi-dts.ts and script-types.d.ts with no diff
• make e2e-cli-update
• live Cargo-installed /script flow with Neovim diagnostics returning no errors