Docs setup

docs/installation.md

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+# Installation Guide
+
+## 🔧 Prerequisites
+
+- **Linux/macOS** (or WSL2 on Windows)
+- AI coding agent: [Claude Code](https://www.anthropic.com/claude-code), [GitHub Copilot](https://code.visualstudio.com/), or [Gemini CLI](https://github.com/google-gemini/gemini-cli)
+- [uv](https://docs.astral.sh/uv/) for package management
+- [Python 3.11+](https://www.python.org/downloads/)
+- [Git](https://git-scm.com/downloads)
+
+## Installation
+
+### Initialize a New Project
+
+The easiest way to get started is to initialize a new project:
+
+```bash
+uvx --from git+https://github.com/github/spec-kit.git specify init <PROJECT_NAME>
+```
+
+Or initialize in the current directory:
+
+```bash
+uvx --from git+https://github.com/github/spec-kit.git specify init --here
+```
+
+### Specify AI Agent
+
+You can proactively specify your AI agent during initialization:
+
+```bash
+uvx --from git+https://github.com/github/spec-kit.git specify init <project_name> --ai claude
+uvx --from git+https://github.com/github/spec-kit.git specify init <project_name> --ai gemini
+uvx --from git+https://github.com/github/spec-kit.git specify init <project_name> --ai copilot
+```
+
+### Ignore Agent Tools Check
+
+If you prefer to get the templates without checking for the right tools:
+
+```bash
+uvx --from git+https://github.com/github/spec-kit.git specify init <project_name> --ai claude --ignore-agent-tools
+```
+
+## Verification
+
+After initialization, you should see the following commands available in your AI agent:
+- `/specify` - Create specifications
+- `/plan` - Generate implementation plans  
+- `/tasks` - Break down into actionable tasks
+
+## 🔍 Troubleshooting
+
+### Git Credential Manager on Linux
+
+If you're having issues with Git authentication on Linux, you can install Git Credential Manager:
+
+```bash
+#!/usr/bin/env bash
+set -e
+echo "Downloading Git Credential Manager v2.6.1..."
+wget https://github.com/git-ecosystem/git-credential-manager/releases/download/v2.6.1/gcm-linux_amd64.2.6.1.deb
+echo "Installing Git Credential Manager..."
+sudo dpkg -i gcm-linux_amd64.2.6.1.deb
+echo "Configuring Git to use GCM..."
+git config --global credential.helper manager
+echo "Cleaning up..."
+rm gcm-linux_amd64.2.6.1.deb
+```