docs: rewrite README in product-page format and add CHANGELOG

README now has: badges (CI, release, license, .NET, stars), live demo
link, problem statement, 30-second YAML example, inputs table,
architecture overview, and development instructions.

CHANGELOG seeded with an [Unreleased] section covering the current
polish pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: TheSmallPixel

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project are documented here.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+- MIT license, contributing guide, issue and PR templates.
+- CI workflow that builds the analyzer and runs xUnit tests on every push and PR.
+- README rewritten in product-page format with badges, inputs table, and architecture overview.
+- `.gitignore` covering .NET, IDE, OS, and editor-backup artifacts.
+
+### Changed
+- Action runtime upgraded to .NET 8 LTS (was .NET 7, out of support).
+- `actions/checkout` and `actions/setup-dotnet` bumped to v4.
+
+### Removed
+- Tracked macOS metadata (`.DS_Store`) and editor backup (`docs/enhanced_visualizer.js.backup`).

README.md

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+<h1 align="center">GraphCSharp</h1>
+
+<p align="center">
+  <strong>Visualize any C# codebase as an interactive D3 graph — drop one GitHub Action into your repo.</strong>
+</p>
+
+<p align="center">
+  <a href="https://github.com/TheSmallPixel/GraphCSharp/actions/workflows/ci.yml"><img src="https://github.com/TheSmallPixel/GraphCSharp/actions/workflows/ci.yml/badge.svg" alt="CI"></a>
+  <a href="https://github.com/TheSmallPixel/GraphCSharp/releases/latest"><img src="https://img.shields.io/github/v/release/TheSmallPixel/GraphCSharp" alt="Release"></a>
+  <a href="LICENSE"><img src="https://img.shields.io/github/license/TheSmallPixel/GraphCSharp" alt="License"></a>
+  <img src="https://img.shields.io/badge/.NET-8.0-512BD4" alt=".NET 8">
+  <a href="https://github.com/TheSmallPixel/GraphCSharp/stargazers"><img src="https://img.shields.io/github/stars/TheSmallPixel/GraphCSharp?style=social" alt="Stars"></a>
+</p>
+
+<p align="center">
+  <a href="https://thesmallpixel.github.io/GraphCSharp/"><strong>→ Open the live demo</strong></a>
+</p>
+
+<!-- TODO(media): replace with docs/demo.gif showing the interactive graph in action -->
+![Demo](docs/demo.gif)
+
+## What it does
+
+Reading C# architecture from a folder tree is slow. Roslyn can extract the real call graph, but wiring it up — analyzer, JSON schema, D3 layout, GitHub Pages — is a side-project of its own. **GraphCSharp is that side-project, packaged as a single GitHub Action so any repo gets an interactive graph on every push.**
+
+## 30-second example
+
+Add `.github/workflows/code-graph.yml` to your repo:
+
+```yaml
+name: Generate Code Graph
+on:
+  push:
+    branches: [main]
+
+permissions:
+  contents: write
+
+jobs:
+  graph:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: TheSmallPixel/GraphCSharp@v1
+        with:
+          source-path: ./src
+          docs-dir: docs
+          commit-changes: 'true'
+```
+
+Then enable GitHub Pages on the `docs/` folder. Your live graph appears at `https://<user>.github.io/<repo>/`.
+
+## Inputs
+
+| Name | Default | Description |
+| --- | --- | --- |
+| `source-path` | `./src` | Directory scanned recursively for `.cs` files. |
+| `docs-dir` | `docs` | Where `graph.json` and `index.html` are written. |
+| `index-file` | `index.html` | Visualizer HTML filename. Copied from this action if missing. |
+| `commit-changes` | `false` | When `true`, commits the generated graph back to your repo. |
+
+## Links
+
+- **Live demo:** https://thesmallpixel.github.io/GraphCSharp/
+- **Changelog:** [CHANGELOG.md](CHANGELOG.md)
+- **Contributing:** [CONTRIBUTING.md](CONTRIBUTING.md)
+- **License:** [LICENSE](LICENSE)
+
+## How it works
+
+1. The action checks out your repo and provisions .NET 8.
+2. Builds the Roslyn-based analyzer in `tools/CodeAnalysisTool`.
+3. Walks every `.cs` file under `source-path`, emitting nodes (namespaces, classes, methods, properties) and links (containment, calls, inheritance, type usage) as `docs/graph.json`.
+4. Drops a D3 visualizer into `docs/index.html` if one isn't already there.
+5. Optionally commits both files back so GitHub Pages serves a fresh graph on every push.
+
+## Development
+
+Requires the .NET 8 SDK.
+
+```bash
+git clone https://github.com/TheSmallPixel/GraphCSharp
+cd GraphCSharp
+dotnet test tools/CodeAnalysisTool.Tests/CodeAnalysisTool.Tests.csproj
+```
+
+To run the analyzer against any folder of `.cs` files:
+
+```bash
+dotnet run --project tools/CodeAnalysisTool -- <source-path> ./docs
+```
+
+Open `docs/index.html` to inspect the result locally.
+
+## License
+
+MIT — see [LICENSE](LICENSE).