function folder/package support (not only single-file functions)

[ashupednekar]

Summary

Support function-as-folder layout instead of single-file functions.

Motivation

Real functions often need multiple files (helpers, schema, assets, dependency manifests). Current single-file model limits maintainability.

Proposal

• Extend function model to allow directory roots, e.g. functions/ts/my_fn/.
• Runtime loader resolves entrypoint (index.ts, main.py, mod.rs, etc.) inside folder.
• Hook sync copies full function directories, not just top-level files.
• Keep single-file mode backward compatible.

Acceptance criteria

• Portal create/update APIs accept folder-based functions.
• Runtimes (at least TS/Python/Lua) load folder entrypoints.
• Existing single-file functions continue to run unchanged.