feat(ai): search + read grounding tools

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/ai/agent/tools/search.js

@@ -0,0 +1,28 @@
+import * as searchRepo from '../../../db/repos/search.js';
+
+export const searchTool = {
+  name: 'search',
+  description: 'Full-text search across pages, refs, source docs and messages in the current Space. Use to find information before answering.',
+  input_schema: {
+    type: 'object',
+    properties: {
+      q: { type: 'string', description: 'search query' },
+      kinds: {
+        type: 'array',
+        items: { type: 'string', enum: ['page', 'ref', 'source_doc', 'message'] },
+        description: 'optional filter of result kinds'
+      }
+    },
+    required: ['q']
+  },
+  async handler({ q, kinds }, ctx) {
+    const results = await searchRepo.fts({
+      q,
+      space_id: ctx.space_id ?? null,
+      kinds: kinds?.length ? kinds : null,
+      limit: 8,
+      offset: 0
+    });
+    return { results };
+  }
+};