feat(kyberforge): enable codex marketplace output

Uncomment marketplace.outputs.codex in apm.yml. Codex output requires
every package to declare a category -- added one per package (Developer
Tools / Utilities / Version Control / Productivity, matching each
plugin's actual scope).

Re-running apm pack after enabling codex auto-synced 'codex' into each
local package's own targets: list (apm.yml, per plugin) -- packages
belonging to a marketplace that publishes a codex output need to declare
codex as a supported compile target for that to be coherent. Verified
idempotent: a second apm pack --check-clean run makes no further changes.

.claude-plugin/marketplace.json regenerated (now carries category per
plugin); .agents/plugins/marketplace.json is the new codex artifact.

Refs: #90

.agents/plugins/marketplace.json

@@ -0,0 +1,95 @@
+{
+  "interface": {
+    "displayName": "holocron"
+  },
+  "name": "holocron",
+  "plugins": [
+    {
+      "category": "Developer Tools",
+      "name": "kyberforge",
+      "policy": {
+        "authentication": "ON_INSTALL",
+        "installation": "AVAILABLE"
+      },
+      "source": {
+        "path": "./plugins/kyberforge",
+        "source": "local"
+      }
+    },
+    {
+      "category": "Utilities",
+      "name": "bin",
+      "policy": {
+        "authentication": "ON_INSTALL",
+        "installation": "AVAILABLE"
+      },
+      "source": {
+        "path": "./plugins/bin",
+        "source": "local"
+      }
+    },
+    {
+      "category": "Version Control",
+      "name": "git",
+      "policy": {
+        "authentication": "ON_INSTALL",
+        "installation": "AVAILABLE"
+      },
+      "source": {
+        "path": "./plugins/git",
+        "source": "local"
+      }
+    },
+    {
+      "category": "Version Control",
+      "name": "gitea",
+      "policy": {
+        "authentication": "ON_INSTALL",
+        "installation": "AVAILABLE"
+      },
+      "source": {
+        "path": "./plugins/gitea",
+        "source": "local"
+      }
+    },
+    {
+      "category": "Productivity",
+      "name": "core",
+      "policy": {
+        "authentication": "ON_INSTALL",
+        "installation": "AVAILABLE"
+      },
+      "source": {
+        "path": "./plugins/core",
+        "source": "local"
+      }
+    },
+    {
+      "category": "Productivity",
+      "name": "mattpocock-skills",
+      "policy": {
+        "authentication": "ON_INSTALL",
+        "installation": "AVAILABLE"
+      },
+      "source": {
+        "ref": "v1.2.3",
+        "sha": "835450ef244ab7335f75d95b83e7d979eae22a6d",
+        "source": "url",
+        "tag_pattern": "v{version}",
+        "url": "mattpocock/skills"
+      }
+    },
+    {
+      "category": "Developer Tools",
+      "name": "lint",
+      "policy": {
+        "authentication": "ON_INSTALL",
+        "installation": "AVAILABLE"
+      },
+      "source": {
+        "path": "./plugins/lint",
+        "source": "local"
+      }
+    }
+  ]
+}