Bug: Plan approval in autopilot+fleet mode triggers execution with fleet dispatch ordering mismatch

## Description

When approving a plan in plan mode while using autopilot+fleet, the plan approval immediately triggers execution AND fleet agent dispatch simultaneously. The "Queued (1)" and "Fleet deployed" messages appear while the main agent is still "Analyzing bugs and planning fixes," suggesting a sequencing/ordering issue between the main agent's work and fleet dispatch.

## Steps to Reproduce

1. Enter plan mode and create a plan (e.g., with multiple bugs/features)
2. Switch to autopilot+fleet mode
3. Copilot recommends committing to the plan with autopilot+fleet
4. Approve/select that recommendation

## Expected Behavior

Plan approval should properly sequence execution — the main agent's analysis should be coordinated with fleet agent dispatch, not race against it.

## Actual Behavior

Fleet dispatch ("Queued (1)", "Fleet deployed") fires concurrently with the main agent beginning its "Analyzing bugs and planning fixes" phase. This ordering mismatch suggests the fleet agents are dispatched before the main agent has finished planning/coordinating the work.

## Screenshot

*(Screenshot shows: Plan approved -> "Analyzing bugs and planning fixes" starts -> "Queued (1)" / "Fleet deployed" messages appear simultaneously)*

## Environment

- OS: Windows
- Copilot CLI version: latest (as of April 2026)
- Mode: Autopilot + Fleet (experimental)

## Additional Context

Also submitted private feedback via the `/feedback` command for internal tracking.

首先在 Windows autopilot+fleet mode 中复现计划审批流程，并跟踪从审批到主代理规划阶段和 Fleet 调度的转换。比较这些操作的顺序，并确定调度在哪里触发。完成的标准是，Fleet 部署与主代理的规划相协调，而不是并发进行，并且报告的状态消息按正确顺序显示。

由索引模型根据 Issue 内容生成。