feat: add install script for Windows PowerShell (#70)

scripts/install_windows.ps1

@@ -0,0 +1,113 @@
+<#
+.SYNOPSIS
+    Install or uninstall the git-workflow skill for Claude Code (Windows).
+
+.DESCRIPTION
+    Creates a symlink so the skill stays in sync with the repo.
+    Symlinks on Windows require either Developer Mode enabled or an
+    elevated (Administrator) terminal.
+
+.PARAMETER Uninstall
+    Remove the skill symlink.
+
+.EXAMPLE
+    .\scripts\install_windows.ps1
+    .\scripts\install_windows.ps1 -Uninstall
+#>
+
+param(
+    [switch]$Uninstall
+)
+
+$ErrorActionPreference = "Stop"
+
+$SkillDir = Join-Path $env:USERPROFILE ".claude\skills\git-workflow"
+$SkillFile = Join-Path $SkillDir "SKILL.md"
+$RepoRoot = Split-Path -Parent (Split-Path -Parent $PSCommandPath)
+$Source = Join-Path $RepoRoot "SKILL.md"
+
+function Write-Info  { param($Msg) Write-Host "  i " -ForegroundColor Blue -NoNewline; Write-Host $Msg }
+function Write-Pass  { param($Msg) Write-Host "  ✓ " -ForegroundColor Green -NoNewline; Write-Host $Msg }
+function Write-Fail  { param($Msg) Write-Host "  ✗ " -ForegroundColor Red -NoNewline; Write-Host $Msg }
+
+function Test-SymlinkSupport {
+    $testDir = Join-Path $env:TEMP "symlink_test_$(Get-Random)"
+    $testLink = Join-Path $env:TEMP "symlink_test_link_$(Get-Random)"
+    try {
+        New-Item -ItemType Directory -Path $testDir -Force | Out-Null
+        New-Item -ItemType SymbolicLink -Path $testLink -Target $testDir -ErrorAction Stop | Out-Null
+        Remove-Item $testLink -Force
+        Remove-Item $testDir -Force
+        return $true
+    } catch {
+        Remove-Item $testDir -Force -ErrorAction SilentlyContinue
+        return $false
+    }
+}
+
+function Invoke-Uninstall {
+    $item = Get-Item $SkillFile -ErrorAction SilentlyContinue
+    if ($item -and $item.Attributes -band [IO.FileAttributes]::ReparsePoint) {
+        Remove-Item $SkillFile -Force
+        Write-Pass "Removed symlink: $SkillFile"
+        # Remove directory if empty
+        if ((Get-ChildItem $SkillDir -ErrorAction SilentlyContinue | Measure-Object).Count -eq 0) {
+            Remove-Item $SkillDir -Force
+            Write-Info "Removed empty directory: $SkillDir"
+        }
+    } elseif ($item) {
+        Write-Fail "$SkillFile exists but is not a symlink — remove it manually to avoid data loss"
+        exit 1
+    } else {
+        Write-Info "Nothing to uninstall — $SkillFile does not exist"
+    }
+    exit 0
+}
+
+function Invoke-Install {
+    # Verify source exists
+    if (-not (Test-Path $Source)) {
+        Write-Fail "SKILL.md not found at $Source"
+        exit 1
+    }
+
+    # Check if already installed
+    $item = Get-Item $SkillFile -ErrorAction SilentlyContinue
+    if ($item -and $item.Attributes -band [IO.FileAttributes]::ReparsePoint) {
+        $currentTarget = $item.Target
+        if ($currentTarget -eq $Source) {
+            Write-Pass "Already installed (symlink points to $Source)"
+            exit 0
+        } else {
+            Write-Info "Existing symlink points to $currentTarget — replacing"
+            Remove-Item $SkillFile -Force
+        }
+    } elseif ($item) {
+        Write-Fail "$SkillFile exists but is not a symlink — remove it manually before installing"
+        exit 1
+    }
+
+    # Check symlink support
+    if (-not (Test-SymlinkSupport)) {
+        Write-Fail "Cannot create symlinks. Enable Developer Mode (Settings > For developers) or run as Administrator."
+        Write-Info "Falling back to file copy (will not auto-sync with repo)."
+        New-Item -ItemType Directory -Path $SkillDir -Force | Out-Null
+        Copy-Item $Source $SkillFile
+        Write-Pass "Installed (copy): $SkillFile"
+        Write-Info "Note: This is a copy, not a symlink. Re-run the installer after updates to sync."
+        exit 0
+    }
+
+    # Create directory and symlink
+    New-Item -ItemType Directory -Path $SkillDir -Force | Out-Null
+    New-Item -ItemType SymbolicLink -Path $SkillFile -Target $Source | Out-Null
+    Write-Pass "Installed: $SkillFile → $Source"
+    Write-Info "The skill will stay in sync with this repo. Restart Claude Code to activate."
+}
+
+# --- Main ---
+if ($Uninstall) {
+    Invoke-Uninstall
+} else {
+    Invoke-Install
+}