Implement clientIO stubs on Shell

[GeorgeNgMsft]

When the shell is connected to an agent-server, agents can now ask the user questions and wait for a response — matching behavior that already existed in the CLI. Previously, any agent-initiated prompt
(yes/no confirmation, multi-choice question) would silently hang for 10 minutes before timing out, because the shell's handlers were unimplemented stubs.

The shell now renders these prompts inline in the chat view using the existing choice panel UI, and correctly handles the multi-client case: if another connected client (e.g. the CLI) answers first, the
shell dismisses its own panel and shows a "[answered by another client]" notice. Server-side cancellations (e.g. timeout) similarly dismiss the panel with an "[interaction cancelled]" notice. Both binary
yes/no and arbitrary multi-choice questions are handled through a single unified code path, consistent with the protocol unification introduced in PR #2194.

[Copilot]

Pull request overview

This PR implements real deferred-interaction handling in the Shell renderer so that, when connected to an agent-server (SharedDispatcher), agent-initiated questions/prompts are rendered inline and can be dismissed when another client answers or when the server cancels the interaction.

Changes:

• Implemented requestInteraction / interactionResolved / interactionCancelled handling in the Shell renderer clientIO to support connected-mode deferred interactions.
• Added ChatView.showInteractionQuestion(...) to render deferred "question" interactions inline via the existing choice panel UI.
• Added a Playwright integration test suite exercising the deferred-interaction UI flow.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
ts/packages/shell/test/interactionUI.spec.ts	New Playwright integration tests for deferred-interaction UI behavior.
ts/packages/shell/src/renderer/src/messageContainer.ts	Exposes the underlying message div to enable inserting/removing choice panels from outside MessageContainer.
ts/packages/shell/src/renderer/src/main.ts	Implements Shell-side deferred interaction handling and wires responses back to the dispatcher.
ts/packages/shell/src/renderer/src/chat/chatView.ts	Adds a unified UI path to render deferred "question" interactions inline using ChoicePanel.

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