feat(plugins): merge Skill management into plugins

tests/unit/pi-extension-bundle.test.ts

@@ -464,7 +464,7 @@ describe('Makelore Pi extension bundle', () => {
     const worker = await host.registerWorker({
       conversationId: 'conversation-tools', generation: 1, projectId: 'project-a',
       projectPath: root,
-      skillEntries: [{ id: 'agent-browser', entryPath: 'agent-browser/SKILL.md' }],
+      skillEntries: [],
       catalogRevision: 3,
       extensionsDir: root,
     });
@@ -507,7 +507,7 @@ describe('Makelore Pi extension bundle', () => {
       )).resolves.toMatchObject({
         details: {
           schema: 'runtime-context.v1',
-          skills: expect.arrayContaining([expect.objectContaining({ id: 'agent-browser', selected: true })]),
+          skills: [],
         },
       });
       const browserResult = await tools.get('agent_browser')?.execute?.(