feat: add setup flow for dedicated research agent

docs/plans/state.json

@@ -3,6 +3,22 @@
   "updated_at": "2026-02-17",
   "description": "Tracks the status of all Flynn plans and implementation phases",
   "plans": {
+    "setup-research-agent-enablement": {
+      "status": "completed",
+      "date": "2026-02-17",
+      "updated": "2026-02-17",
+      "summary": "Extended setup Security flow to provision a dedicated research sub-agent (`agent_configs.research`) with selectable tier, so `/research` and research-prefix auto-routing work immediately after setup. Added builder/test coverage and documented optional explicit intents routing example in default config.",
+      "files_modified": [
+        "src/cli/setup/config.ts",
+        "src/cli/setup/security.ts",
+        "src/cli/setup/config.test.ts",
+        "src/cli/setup/sections.test.ts",
+        "config/default.yaml",
+        "README.md",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/cli/setup/config.test.ts src/cli/setup/sections.test.ts passing + pnpm typecheck passing"
+    },
     "research-prefix-auto-routing": {
       "status": "completed",
       "date": "2026-02-17",