docs (CLAUDE.md): add llm instructions

Author: pythoninthegrass

CLAUDE.md

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+# meetup_bot Project Reference
+
+## General Instructions
+
+- Minimize inline comments
+- Retain tabs, spaces, and encoding
+- Fix linting errors before saving files.
+  - Respect `.markdownlint.jsonc` rules for all markdown files
+- If under 50 lines of code (LOC), print the full function or class
+- If the token limit is close or it's over 50 LOC, print the line numbers and avoid comments altogether
+- Explain as much as possible in the chat unless asked to annotate (i.e., docstrings, newline comments, etc.)
+
+## Build, Lint, and Test Commands
+
+- Full test suite: `uv run pytest` or `task test`
+- Single test: `uv run pytest tests/test_filename.py::test_function_name`
+- Linting: `uv run ruff check --fix --respect-gitignore` or `task lint`
+- Formatting: `uv run ruff format --respect-gitignore` or `task format`
+- Check dependencies: `uv run deptry .` or `task deptry`
+- Pre-commit hooks: `pre-commit run --all-files` or `task pre-commit`
+
+## Code Style Guidelines
+
+- **Formatting**: 4 spaces, 130-char line limit, LF line endings
+- **Imports**: Ordered by type, combined imports when possible
+- **Naming**: snake_case functions/vars, PascalCase classes, UPPERCASE constants
+- **Type Hints**: Use Optional for nullable params, pipe syntax for Union
+- **Error Handling**: Specific exception types, descriptive error messages
+- **File Structure**: Core logic in app/core/, utilities in app/utils/
+- **Docstrings**: Use double quotes for docstrings
+- **Tests**: Files in tests/, follow test_* naming convention