add CLAUDE.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: v1rtl

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Deno port of Apollo's graphql-tag library. Provides a `gql` template literal function that parses GraphQL schema definitions into AST DocumentNode objects with caching.
+
+## Development Commands
+
+```bash
+# Run tests with coverage
+deno task test
+
+# Generate LCOV coverage report
+deno task cov
+
+# Format code
+deno fmt
+
+# Lint code
+deno lint
+```
+
+## Code Style
+
+- Single quotes, no semicolons
+- 2-space indentation, 120-char line width
+- TypeScript throughout
+
+## Architecture
+
+**mod.ts** - Single-file library containing:
+- `gql()` template literal function (main export)
+- Document caching by normalized source text
+- Fragment deduplication with warnings for conflicting definitions
+- AST location stripping for memory efficiency
+- Utility functions: `resetCaches()`, `disableFragmentWarnings()`, `enableExperimentalFragmentVariables()`
+
+**deps.ts** - External dependencies from esm.sh (GraphQL 16.8.1)
+
+**mod_test.ts** - Tests using tincan framework