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/persist.ts

@@ -0,0 +1,35 @@
+// TokenScope persistence — writes breakdown to task records.
+import type { Sql } from '../../db.js';
+import type { TokenBreakdown } from './analyzer.js';
+
+export async function persistTaskBreakdown(
+  sql: Sql,
+  taskId: string,
+  breakdown: TokenBreakdown,
+): Promise<void> {
+  await sql`
+    UPDATE tasks SET token_breakdown = ${sql.json(breakdown as never)}
+    WHERE id = ${taskId}
+  `;
+}
+
+export async function getTaskBreakdown(
+  sql: Sql,
+  taskId: string,
+): Promise<TokenBreakdown | null> {
+  const rows = await sql<{ token_breakdown: any }[]>`
+    SELECT token_breakdown FROM tasks WHERE id = ${taskId}
+  `;
+  return rows[0]?.token_breakdown ?? null;
+}
+
+export async function analyzeAndPersistTaskBreakdown(
+  sql: Sql,
+  taskId: string,
+  parts: any[],
+): Promise<TokenBreakdown> {
+  const { analyzeMessages } = await import('./analyzer.js');
+  const breakdown = analyzeMessages(parts);
+  await persistTaskBreakdown(sql, taskId, breakdown);
+  return breakdown;
+}