Add external plugin copilot-goal-skill (#1950)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

.github/plugin/marketplace.json

@@ -159,6 +159,31 @@
       "description": "Coding agents hallucinate APIs. ContextMatic gives them curated, versioned API and SDK docs. Ask your agent to \"integrate the payments API\" and it guesses — falling back on outdated training data and generic patterns that don't match your actual SDK. ContextMatic solves this by giving the agent deterministic, version-aware, SDK-native context at the exact moment it's needed.",
       "version": "0.1.0"
     },
+    {
+      "name": "copilot-goal-skill",
+      "description": "Goal-driven task orchestration with independent verification. Interviews the user to define a clear goal, then loops between a Builder subagent (does the work) and an Inspector subagent (judges the result with fresh context). The Inspector never trusts the Builder. Output is auditable in git commits from each subagent actions. Use when the user says \"achieve this goal\", \"make this work\", \"implement until done\", or wants verified autonomous task completion with independent quality review.",
+      "version": "1.0.1",
+      "author": {
+        "name": "Gaetan Semet",
+        "url": "https://github.com/gsemet"
+      },
+      "repository": "https://github.com/gsemet/copilot-goal-skill",
+      "license": "MIT",
+      "keywords": [
+        "goal",
+        "autonomous",
+        "inspector",
+        "builder",
+        "loop"
+      ],
+      "source": {
+        "source": "github",
+        "repo": "gsemet/copilot-goal-skill",
+        "path": "plugins/copilot-goal-skill",
+        "ref": "1.0.1",
+        "sha": "b186d0b0d59da1ea051283a7d99185979ede998a"
+      }
+    },
     {
       "name": "copilot-sdk",
       "source": "copilot-sdk",