fix: restore skill creator script entry points

[one241]

Summary

• restore the documented main(args) entry point for all built-in skill creator scripts
• guard the optional CommonJS fallback so missing entry points report the intended error instead of ReferenceError: module is not defined
• add regression coverage that keeps all built-in script entry points aligned with the QuickJS runner

Root cause

The scripts exposed _main(args), while the QuickJS runner only invokes main(args) or module.exports. Biome treats the runtime-invoked main function as statically unused and suggests prefixing it with an underscore, so the entry points now include explicit lint suppressions explaining the runtime contract.

Testing

• pnpm exec biome check ...
• pnpm -r --if-present typecheck
• pnpm -r --if-present test
• pre-push fix end of files and typos hooks

[buttercannfly]

@jk4235 could you review this?