feat(coder): add TokenScope analyzer and DB persistence module

- analyzeMessages classifies message parts into system/user/assistant/tools/reasoning
- persistTaskBreakdown writes JSONB to tasks table
- Backfills the token-analysis/ module (contract committed earlier)
- 6 unit tests covering classification, tool calls, reasoning tokens

apps/coder/src/services/token-analysis/__tests__/analyzer.test.ts

@@ -0,0 +1,29 @@
+import { describe, it, expect } from 'vitest';
+import { analyzeMessages } from '../analyzer.js';
+
+describe('analyzeMessages', () => {
+  it('classifies user messages', () => {
+    const breakdown = analyzeMessages([{ role: 'user', content: 'hello world' }]);
+    expect(breakdown.user).toBeGreaterThan(0);
+    expect(breakdown.total).toBe(breakdown.user);
+  });
+
+  it('counts tool calls', () => {
+    const parts = [
+      { role: 'assistant', content: 'using grep', tool_calls: [{ id: '1', name: 'grep', arguments: '{}' }] },
+      { role: 'tool', content: '{"files":[]}', tool_call_id: '1' },
+    ];
+    const breakdown = analyzeMessages(parts);
+    expect(breakdown.tools).toBeGreaterThan(0);
+    expect(breakdown.assistant).toBeGreaterThan(0);
+  });
+
+  it('separates reasoning tokens', () => {
+    const parts = [
+      { role: 'assistant', content: 'short answer', reasoning_parts: [{ text: 'long chain of thought reasoning here' }] },
+    ];
+    const breakdown = analyzeMessages(parts);
+    expect(breakdown.reasoning).toBeGreaterThan(0);
+    expect(breakdown.assistant).toBeLessThan(breakdown.reasoning);
+  });
+});