Fix Agent Host chat picker disposal

[roblourens]

Summary

• cancel the initial session-config resolve when the Agent Host chat input picker is disposed
• guard late chip renders after the picker render store has been disposed

Validation

• npm run typecheck-client
• npm run gulp compile
• ./scripts/test.sh --runGlob '**/agentHostChatInputPicker.test.js'
• npm run valid-layers-check

(Written by Copilot)

[Copilot]

Pull request overview

This PR fixes lifecycle/disposal edge cases in the workbench chat “Agent Host” input picker so that async session-config resolution and late UI updates don’t run after the picker has been disposed.

Changes:

• Cancel any in-flight initial resolveSessionConfig work when the picker is disposed.
• Guard _renderChip() against late invocations after the render disposable store has already been disposed.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/agentHostChatInputPicker.ts	Ensures picker disposal cancels initial config resolution and prevents late chip renders after disposal.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0