Add Claude Desktop extensions (.mcpb) for WordCraft and GridCraft.

Ship unsigned MCPB packages built from the ArtCraft Launcher CLIs, with install docs and skill 0.2.0 updates.

scripts/package-all.ps1

@@ -0,0 +1,14 @@
+# Builds ZIP for every skill and .mcpb when skills\<name>\extension\ exists.
+# Usage: scripts\package-all.ps1
+. (Join-Path $PSScriptRoot 'lib.ps1')
+
+& (Join-Path $PSScriptRoot 'package.ps1')
+if ($LASTEXITCODE -ne 0) { exit 1 }
+
+foreach ($n in (Get-SkillNames)) {
+    $ext = Join-Path (Join-Path $SkillsDir $n) 'extension\manifest.json'
+    if (Test-Path $ext) {
+        & (Join-Path $PSScriptRoot 'package-mcpb.ps1') -Name $n
+        if ($LASTEXITCODE -ne 0) { exit 1 }
+    }
+}