Migrate plugins and canvas extensions to Agent Plugins spec (#2546)

* feat: migrate plugins and extensions to Agent Plugins v1.0.0 spec

- Add \ to all 69 curated plugin manifests
- Migrate all 18 extension manifests: add \, move logo into
  xtensions.com.github.copilot.logo namespace, remove top-level
  logo and string xtensions: '.'
- Update eng/validate-plugins.mjs: require \, validate
  namespace-keyed extensions object for canvas extensions, widen
  name pattern to allow dots (spec §5.5, max 64 chars)
- Update eng/materialize-plugins.mjs: emit spec-clean served manifests
  (only spec fields: \, name, version, description, author,
  homepage, repository, license, keywords, extensions)
- Update eng/generate-website-data.mjs: read logo from namespace
  with fallback to top-level logo for compatibility
- Update eng/create-plugin.mjs: scaffold emits \
- Add .github/workflows/validate-plugins.yml: blocking CI for PRs
  touching plugins/** or extensions/**
- Add spec compliance check to external plugin quality gates:
  non-blocking warnings with ✅/⚠️/🛑 emoji legend
- Update AGENTS.md: document new extension manifest shape,
  add \ to plugin checklist

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* refactor: consolidate canvas extension plugins

- Move all extension plugin manifests from extensions/<name> to plugins/<name>
- Keep extensions/<name> as reusable source only
- Remove standalone extension discovery from marketplace and website plugin catalogs
- Auto-bundle same-name extension sources during materialization
- Add build-only extensions.json references for sharing extensions across plugins
- Remove x-awesome-copilot extension metadata support
- Update validation and contributor documentation

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* feat: add canvas extension scaffolding skill

- Add repo-local skill for creating canvas extension sources
- Generate spec-compliant plugin manifests under plugins/
- Support registering reusable extensions with multiple plugins
- Remove guidance for extension-local plugin manifests and custom fields

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* fix: align extension namespaces with current guidance

- Use each extension ID as its manifest namespace key
- Update validation and website generation to resolve extension-specific namespaces
- Upsert plugin validation PR comments using the existing repository pattern

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* fix: use Copilot extension namespace

- Adopt com.github.copilot for all canvas extension manifests
- Require the namespace during validation and website generation
- Update extension scaffolding guidance

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* docs: regenerate plugin catalog after merge

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* refactor(plugins): move manifests to plugin roots

Use root plugin.json manifests and namespaced extension directories throughout local tooling, validation, generation, and contributor documentation. Restore materialize-plugins.mjs line breaks so the source remains readable in GitHub.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* feat(plugins): migrate manifests to namespaced composition

Move repository composition metadata under com.github.awesome-copilot, materialize reusable extensions into the plugin extensions directory, and improve contributor and PR validation guidance.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* fix(validation): address plugin review findings

Restore executable build scripts, validate namespaced manifests and hook directories, improve README item counts, and manage validation comments across reruns.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Copilot-Session: 8f3a88cb-e01e-4760-8125-460490dc1a76

eng/generate-marketplace.mjs

@@ -2,11 +2,11 @@
 
 import fs from "fs";
 import path from "path";
+import { fileURLToPath } from "url";
 import { ROOT_FOLDER } from "./constants.mjs";
 import { readExternalPlugins } from "./external-plugin-validation.mjs";
 
 const PLUGINS_DIR = path.join(ROOT_FOLDER, "plugins");
-const EXTENSIONS_DIR = path.join(ROOT_FOLDER, "extensions");
 const MARKETPLACE_FILE = path.join(ROOT_FOLDER, ".github/plugin", "marketplace.json");
 
 /**
@@ -15,7 +15,7 @@ const MARKETPLACE_FILE = path.join(ROOT_FOLDER, ".github/plugin", "marketplace.j
  * @returns {object|null} - Plugin metadata or null if not found
  */
 function readPluginMetadata(pluginDir) {
-  const pluginJsonPath = path.join(pluginDir, ".github/plugin", "plugin.json");
+  const pluginJsonPath = path.join(pluginDir, "plugin.json");
 
   if (!fs.existsSync(pluginJsonPath)) {
     console.warn(`Warning: No plugin.json found for ${path.basename(pluginDir)}`);
@@ -62,35 +62,18 @@ function collectLocalPluginsFromRoot(rootDir, sourcePrefix, includeEntry = () =>
   return plugins;
 }
 
-function hasExtensionEntryPoint(extensionDir, extensionName) {
-  const candidateEntryPoints = [
-    path.join(extensionDir, "extension.mjs"),
-    path.join(extensionDir, "extensions", "extension.mjs"),
-    path.join(extensionDir, "extensions", extensionName, "extension.mjs"),
-  ];
-
-  return candidateEntryPoints.some((entryPointPath) => fs.existsSync(entryPointPath));
-}
-
 /**
  * Generate marketplace.json from plugin directories
  */
-function generateMarketplace() {
+export function generateMarketplace() {
   console.log("Generating marketplace.json...");
 
-  if (!fs.existsSync(PLUGINS_DIR) && !fs.existsSync(EXTENSIONS_DIR)) {
-    console.error(`Error: Neither plugins directory (${PLUGINS_DIR}) nor extensions directory (${EXTENSIONS_DIR}) was found`);
+  if (!fs.existsSync(PLUGINS_DIR)) {
+    console.error(`Error: Plugins directory (${PLUGINS_DIR}) was not found`);
     process.exit(1);
   }
 
-  const plugins = [
-    ...collectLocalPluginsFromRoot(PLUGINS_DIR, "plugins"),
-    ...collectLocalPluginsFromRoot(
-      EXTENSIONS_DIR,
-      "extensions",
-      (entryName) => hasExtensionEntryPoint(path.join(EXTENSIONS_DIR, entryName), entryName)
-    )
-  ];
+  const plugins = collectLocalPluginsFromRoot(PLUGINS_DIR, "plugins");
 
   console.log(`Found ${plugins.length} local plugin manifests`);
 
@@ -144,5 +127,6 @@ function generateMarketplace() {
   console.log(`  Location: ${MARKETPLACE_FILE}`);
 }
 
-// Run the script
-generateMarketplace();
+if (process.argv[1] && path.resolve(process.argv[1]) === fileURLToPath(import.meta.url)) {
+  generateMarketplace();
+}