v2.0.5: FAST_MODEL routing + tool-use summaries + Qwen dispatch + Arena

Source-level recon of QwenLM/qwen-code (Apache-2.0) informed 4 lifts:

1. FAST_MODEL config: optional env var routes cheap LLM calls (titles,
   summaries, labeling) to a smaller model on llama-swap. auto_name.ts
   uses ctx.config.FAST_MODEL ?? session.model. Set FAST_MODEL=nemotron-
   nano-4b to avoid loading the 35B model for 20-token title generation.

2. Tool-use summaries (services/inference/tool-summaries.ts): utility
   that generates "git-commit-subject-style" labels for tool batches via
   a fast-model LLM call. System prompt + truncation logic ported from
   Qwen Code's toolUseSummary.ts. Exported via @boocode/server/inference
   for BooCoder's dispatcher to call after task completion.

3. Qwen as dispatchable agent: added to agent-probe.ts KNOWN_AGENTS.
   PTY dispatch builds: qwen -p "<task>" --output-format stream-json
   (NDJSON structured events over stdout). Env: OPENAI_BASE_URL +
   OPENAI_API_KEY points Qwen Code at llama-swap. execution_path CHECK
   constraint extended with 'qwen'.

4. Arena routes (routes/arena.ts): POST /api/arena dispatches the same
   task to N contestants (2-5, each with different agent/model), each
   getting its own task row linked by arena_id UUID. GET /api/arena/:id
   shows all contestants. POST /api/arena/:id/select/:task_id marks
   winner. Schema: arena_id column added to tasks.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/coder/src/schema.sql

@@ -31,7 +31,7 @@ CREATE TABLE IF NOT EXISTS tasks (
   ended_at TIMESTAMPTZ,
   created_at TIMESTAMPTZ NOT NULL DEFAULT clock_timestamp(),
   CONSTRAINT tasks_state_chk CHECK (state IN ('pending', 'running', 'completed', 'failed', 'blocked', 'cancelled')),
-  CONSTRAINT tasks_execution_path_chk CHECK (execution_path IS NULL OR execution_path IN ('native', 'acp', 'pty'))
+  CONSTRAINT tasks_execution_path_chk CHECK (execution_path IS NULL OR execution_path IN ('native', 'acp', 'pty', 'qwen'))
 );
 
 CREATE TABLE IF NOT EXISTS available_agents (
@@ -46,6 +46,18 @@ CREATE TABLE IF NOT EXISTS available_agents (
 -- v2.0.0 Phase 4: link tasks to their inference sessions.
 ALTER TABLE tasks ADD COLUMN IF NOT EXISTS session_id UUID REFERENCES sessions(id);
 
+-- v2.0.5: add 'qwen' to execution_path CHECK + arena_id column.
+ALTER TABLE tasks DROP CONSTRAINT IF EXISTS tasks_execution_path_chk;
+DO $$ BEGIN
+  IF NOT EXISTS (SELECT 1 FROM pg_constraint WHERE conname = 'tasks_execution_path_chk') THEN
+    ALTER TABLE tasks ADD CONSTRAINT tasks_execution_path_chk
+      CHECK (execution_path IS NULL OR execution_path IN ('native', 'acp', 'pty', 'qwen'));
+  END IF;
+END $$;
+
+-- v2.0.5: arena support — group tasks into competitive arenas.
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS arena_id UUID;
+
 -- Human inbox: tasks needing attention
 CREATE OR REPLACE VIEW human_inbox AS
   SELECT * FROM tasks WHERE state IN ('blocked', 'failed');