feat(server): skills v1 — parser, tools, /api/skills, mount

- /data/skills mount (host: /opt/skills)
- skill_find, skill_use, skill_resource added to default read-only
  tool set; opt-in for agents with explicit tools: whitelist
- AGENTS.md builtin agents drop explicit tools: arrays to inherit
  the new default (now includes skill tools)
- POST /api/chats/:id/skill_invoke for slash-command flow
- 19 SKILL.md files seeded at /opt/skills/ across 6 source groups

apps/server/src/index.ts

@@ -15,8 +15,10 @@ import { registerSidebarRoutes } from './routes/sidebar.js';
 import { registerWebSocket } from './routes/ws.js';
 import { registerModelRoutes } from './routes/models.js';
 import { registerAgentRoutes } from './routes/agents.js';
+import { registerSkillsRoutes } from './routes/skills.js';
 import { createInferenceRunner } from './services/inference.js';
 import { createBroker } from './services/broker.js';
+import { listSkills } from './services/skills.js';
 
 async function main() {
   const config = loadConfig();
@@ -62,6 +64,15 @@ async function main() {
   registerSidebarRoutes(app, sql);
   registerChatRoutes(app, sql, broker);
 
+  // Batch 9.6: warm the skills cache at boot and surface the count. Empty or
+  // missing /data/skills is non-fatal — the skill tools just return empty.
+  try {
+    const skills = await listSkills();
+    app.log.info(`skills loaded: ${skills.length}`);
+  } catch (err) {
+    app.log.warn({ err }, 'skills boot walk failed');
+  }
+
   const inference = createInferenceRunner(
     {
       sql,
@@ -113,6 +124,33 @@ async function main() {
       });
     },
   });
+  registerSkillsRoutes(app, sql, {
+    enqueueInference: (sessionId, chatId, assistantId, user) => {
+      inference.enqueue(sessionId, chatId, assistantId, user);
+    },
+    publishUserMessage: (sessionId, chatId, userMessageId, content) => {
+      broker.publish(sessionId, {
+        type: 'message_started',
+        message_id: userMessageId,
+        chat_id: chatId,
+        role: 'user',
+      });
+      broker.publish(sessionId, {
+        type: 'delta',
+        message_id: userMessageId,
+        chat_id: chatId,
+        content,
+      });
+      broker.publish(sessionId, {
+        type: 'message_complete',
+        message_id: userMessageId,
+        chat_id: chatId,
+      });
+    },
+    publishSessionFrame: (sessionId, frame) => {
+      broker.publish(sessionId, frame);
+    },
+  });
   registerWebSocket(app, sql, broker);
 
   const webDist = process.env.WEB_DIST_PATH ?? resolve(process.cwd(), '../web/dist');