docs: Add CLAUDE.md to document build, test, code style, project conventions, and environment.

Author: tercel

CLAUDE.md

@@ -0,0 +1,32 @@
+# CLAUDE.md — apcore-cli-typescript
+
+## Build & Test
+
+- `pnpm test` (or `npx vitest run`) — run all tests. **Must pass before considering any task complete.**
+- `pnpm build` — compile TypeScript to `dist/`.
+- `npx tsc --noEmit` — type check without emitting.
+
+## Code Style
+
+- TypeScript strict mode with full type coverage.
+- All code must pass `tsc --noEmit` with zero errors.
+- Use `process.stderr.write()` for error output, `process.stdout.write()` or `console.log()` for normal output.
+- Prefer `process.exit(code)` with `EXIT_CODES` constants over throwing for CLI errors.
+- camelCase for functions/methods/variables, PascalCase for classes/interfaces/types.
+
+## Project Conventions
+
+- Spec repo (single source of truth): `../apcore-cli/docs/`
+- Python reference implementation: `../apcore-cli-python/`
+- ESM module (`"type": "module"` in package.json).
+- Public API exported from `src/index.ts`.
+- CLI framework: Commander.js (not Click or clap).
+- DEFAULTS keys use snake_case dot-notation to match spec (e.g., `cli.help_text_max_length`, not `cli.helpTextMaxLength`).
+- Security modules live in `src/security/` sub-directory.
+- Tests: vitest, files in `tests/*.test.ts`.
+
+## Environment
+
+- Node.js >= 18
+- Package manager: pnpm
+- Key dependencies: commander, js-yaml, ajv