feat: add per-cron-job model tier selection

Allow cron jobs to specify a `model_tier` field that controls which LLM
tier handles the job, without needing separate agent configs. Precedence:
cron job model_tier > agent config > global primary_tier > 'default'.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/daemon/routing.test.ts

@@ -1,6 +1,7 @@
 import { describe, it, expect } from 'vitest';
 import { AgentRouter } from '../agents/router.js';
 import { AgentConfigRegistry } from '../agents/registry.js';
+import type { ModelTier } from '../models/router.js';
 
 describe('daemon agent routing integration', () => {
   it('resolves agent config for channel messages', () => {
@@ -35,4 +36,28 @@ describe('daemon agent routing integration', () => {
     const router = new AgentRouter({ channels: {}, senders: {} });
     expect(router.resolve('telegram', '123')).toBeUndefined();
   });
+
+  it('model tier precedence: metadata > agent config > global default', () => {
+    // This test documents the tier resolution precedence used by createMessageRouter.
+    // The actual resolution logic: tierFromMetadata ?? agentConfig?.modelTier ?? primary_tier ?? 'default'
+    function resolveTier(
+      metadataTier: ModelTier | undefined,
+      agentTier: ModelTier | undefined,
+      globalTier: ModelTier | undefined,
+    ): ModelTier {
+      return metadataTier ?? agentTier ?? globalTier ?? 'default';
+    }
+
+    // With all three set, metadata wins
+    expect(resolveTier('fast', 'complex', 'default')).toBe('fast');
+
+    // Without metadata, agent config wins
+    expect(resolveTier(undefined, 'complex', 'default')).toBe('complex');
+
+    // Without metadata or agent config, global wins
+    expect(resolveTier(undefined, undefined, 'default')).toBe('default');
+
+    // Without anything, falls back to 'default'
+    expect(resolveTier(undefined, undefined, undefined)).toBe('default');
+  });
 });