[VS Code Shell] Update permissions request UX

[George Ng (GeorgeNgMsft)]

Summary

Permission requests now appear in a popup above the chat instead of interrupting the conversation. Users can approve a tool once, for the current request, or for the session. The new @allow all and @allow off commands, along with natural-language equivalents, control session permissions. A shared reasoning permission policy has also been introduced to unify the behaviors across reasoning providers (like Claude or Copilot).

• Copilot and Claude reasoning providers use the same host permission policy and popup.
• Multiple requests are queued in one popup and can be viewed with the arrow controls.
• Choosing an option only updates the Allow button; nothing runs until the button is clicked.
• @allow all allows eligible tools for either reasoning provider in the current TypeAgent session. @allow off resets those session permissions.
• Prompts show what the provider wants to run. Safety, sandbox, and policy-controlled actions still require explicit approval.
• Pending prompts recover after reconnects and are cleared when switching conversations.
• The granted permission is shown as a short note on the final response instead of another chat message.

Normal clarification and semantic confirmation questions still appear in the chat and are not bypassed by @allow all.

Screenshots

System-authored questions continue to appear in the chat: