refactor: remove SERVICE_AGENT_TYPE legacy constant

SERVICE_AGENT_TYPE was always 'claude-code' in the unified service,
making it a misleading constant. Each group already has its own
agentType field.

- Removed SERVICE_AGENT_TYPE from config.ts
- Session functions now accept agentType parameter (default: 'claude-code')
- Task scheduler uses task-level agent_type for token rotation decisions
- All fallback defaults changed to 'claude-code' literal
- Logging uses 'unified' instead of the misleading type

setup/register.ts

@@ -9,7 +9,7 @@ import path from 'path';
 
 import Database from 'better-sqlite3';
 
-import { SERVICE_AGENT_TYPE, STORE_DIR } from '../src/config.js';
+import { STORE_DIR } from '../src/config.js';
 import { isValidGroupFolder } from '../src/group-folder.js';
 import { logger } from '../src/logger.js';
 import { emitStatus } from './status.js';
@@ -156,7 +156,7 @@ export async function run(args: string[]): Promise<void> {
     timestamp,
     requiresTriggerInt,
     isMainInt,
-    SERVICE_AGENT_TYPE,
+    'claude-code',
   );
 
   db.close();