Add Copilot Workshops sync workflow + Learning Hub i18n (#2325)

Adds an agentic (gh-aw) workflow that mirrors the multi-harness workshop
from github-samples/copilot-workshops into the Learning Hub, plus the
Starlight infrastructure it needs: GitHub-admonition rendering, i18n
locales with English at the site root, and a language picker that only
appears when a page has a non-English translation.


Copilot-Session: 9e1d1a4c-a422-4cae-8ea7-b3d5171f58e3

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

website/package-lock.json

@@ -18,6 +18,7 @@
         "isomorphic-dompurify": "^2.36.0",
         "jszip": "^3.10.1",
         "marked": "^18.0.2",
+        "remark-github-admonitions-to-directives": "^2.1.0",
         "shiki": "^4.0.2"
       },
       "devDependencies": {
@@ -6491,6 +6492,21 @@
         "url": "https://opencollective.com/unified"
       }
     },
+    "node_modules/remark-github-admonitions-to-directives": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/remark-github-admonitions-to-directives/-/remark-github-admonitions-to-directives-2.1.0.tgz",
+      "integrity": "sha512-bI3E4Oj1pKY3ym2IQrrVCdORgEu0+mSrWgpCYFNy8QvytfnLs/nAacVPjkWU/JzDMUiQio2k4nTFP7bsIr9TSA==",
+      "license": "MIT",
+      "dependencies": {
+        "@types/mdast": "^4.0.0",
+        "mdast-util-directive": "^3.0.0",
+        "unified": "^11.0.0",
+        "unist-util-visit": "^5.0.0"
+      },
+      "engines": {
+        "pnpm": ">=9.0.0"
+      }
+    },
     "node_modules/remark-mdx": {
       "version": "3.1.1",
       "resolved": "https://registry.npmjs.org/remark-mdx/-/remark-mdx-3.1.1.tgz",