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__/persist.test.ts

@@ -0,0 +1,10 @@
+import { describe, it, expect } from 'vitest';
+
+describe('persistTaskBreakdown', () => {
+  it('exports functions', async () => {
+    const mod = await import('../persist.js');
+    expect(typeof mod.persistTaskBreakdown).toBe('function');
+    expect(typeof mod.getTaskBreakdown).toBe('function');
+    expect(typeof mod.analyzeAndPersistTaskBreakdown).toBe('function');
+  });
+});