chore(core): bump version to 1.1.0 for new skill content

core gained three skills for the first time (agentsmd-author,
agentsmd-audit, provider-adapter-author). Minor bump reflects new
capability rather than a fix. Also declares the missing `skills`
path in the Copilot manifest so Copilot CLI discovers them
(CC auto-discovers from the plugin root; Copilot requires explicit
declaration per ADR-0016 convention).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

plugins/core/.claude-plugin/plugin.json

@@ -14,5 +14,5 @@
   ],
   "license": "MIT",
   "name": "core",
-  "version": "1.0.0"
+  "version": "1.1.0"
 }

plugins/core/plugin.json

@@ -15,5 +15,8 @@
   "license": "MIT",
   "mcpServers": ".mcp.json",
   "name": "core",
-  "version": "1.0.0"
+  "skills": [
+    "skills/"
+  ],
+  "version": "1.1.0"
 }