Add CLAUDE.md with project guidance for Claude Code (#2)

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.
+
+## Build and Run Commands
+
+```bash
+# Build the binary
+go build -o rollup .
+
+# Run directly
+go run main.go [command]
+
+# Run tests
+go test ./...
+
+# Run a single test
+go test -run TestName ./path/to/package
+```
+
+## Project Overview
+
+Rollup is a Go CLI tool that aggregates text-based files and webpages into markdown files. It has three main commands:
+- `files` - Rolls up local files into a single markdown file
+- `web` - Scrapes webpages and converts to markdown using Playwright
+- `generate` - Creates a default rollup.yml config file
+
+## Architecture
+
+**Entry Point**: `main.go` initializes Playwright browser and loads config before executing commands via Cobra.
+
+**Command Layer** (`cmd/`):
+- `root.go` - Cobra root command with global flags (--config, --verbose)
+- `files.go` - File aggregation with glob pattern matching for ignore/codegen detection
+- `web.go` - Web scraping orchestration, converts config site definitions to scraper configs
+- `generate.go` - Scans directory for text file types and generates rollup.yml
+
+**Internal Packages**:
+- `internal/config` - YAML config loading and validation. Defines `Config`, `SiteConfig`, `PathOverride` structs
+- `internal/scraper` - Playwright-based web scraping with rate limiting, HTML-to-markdown conversion via goquery and html-to-markdown library
+
+**Key Dependencies**:
+- `spf13/cobra` - CLI framework
+- `playwright-go` - Browser automation for web scraping
+- `PuerkitoBio/goquery` - HTML parsing and CSS selector extraction
+- `JohannesKaufmann/html-to-markdown` - HTML to markdown conversion
+
+## Configuration
+
+The tool reads from `rollup.yml` by default. Key config fields:
+- `file_extensions` - File types to include in rollup
+- `ignore_paths` / `code_generated_paths` - Glob patterns for exclusion
+- `sites` - Web scraping targets with CSS selectors, path filtering, rate limiting