readmes and mds plus fixed ruff

CONTRIBUTING.md

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+# Contributing to ForeignThon
+
+## Project structure
+foreignthon/
+├── packages/
+│   ├── foreignthon/          # core engine + fpy CLI
+│   │   ├── src/foreignthon/
+│   │   │   ├── cli.py        # fpy commands
+│   │   │   ├── transpiler.py # tokenizer-based transpiler
+│   │   │   ├── pack.py       # language pack loader
+│   │   │   └── errors.py     # bilingual error hook
+│   │   └── tests/
+│   └── langs/
+│       └── es/               # Spanish language pack
+│           └── src/foreignthon_es/es.json
+
+## Setting up
+
+```bash
+python -m venv .venv && source .venv/bin/activate
+pip install -e "packages/foreignthon[dev]"
+pip install -e packages/langs/es
+```
+
+## Running tests
+
+```bash
+pytest packages/foreignthon/tests/ -v
+```
+
+## Adding a new language pack
+
+1. Copy `packages/langs/es/` to `packages/langs/<code>/`
+2. Rename `foreignthon_es` → `foreignthon_<code>` throughout
+3. Fill in `<code>.json` following the same schema as `es.json`
+4. Validate it: `fpy pack packages/langs/<code>/src/foreignthon_<code>/<code>.json`
+5. Add tests if the language has tricky characters or edge cases
+6. Open a PR or publish independently as `foreignthon-<code>` on PyPI
+
+## Language pack schema
+
+Every pack must have these top-level keys:
+`meta`, `keywords`, `builtins`, `exceptions`, `error_messages`, `stdlib`
+
+See `packages/langs/es/src/foreignthon_es/es.json` as the reference.
+
+## Code style
+
+```bash
+ruff check packages/foreignthon/src
+```