refactor: remove unused imports, variables, and constants

- inner-loop-tracker.ts: Comment out unused COMPLETION_SIGNAL_PATTERN, use _id
- session.ts: Remove unused execSync import and timeout constants
- task-tracker.ts: Use _context for unused parameter
- server.ts: Remove unused FastifyRequest import

All files now pass --noUnusedLocals --noUnusedParameters check.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/task-tracker.ts

@@ -367,7 +367,7 @@ export class TaskTracker extends EventEmitter {
    * @param context - Terminal context for debugging
    * @fires taskCreated
    */
-  private createTaskFromTerminal(agentType: string, context: string): void {
+  private createTaskFromTerminal(agentType: string, _context: string): void {
     const taskId = `terminal-${Date.now()}-${Math.random().toString(36).substr(2, 9)}`;
     const parentId = this.taskStack.length > 0 ? this.taskStack[this.taskStack.length - 1] : null;