[Feature Request] Add `promptStyle` config option for rate-limit/decision prompts

Bug Description
Title: Add config to choose between modal and chat-message style for rate-limit /
decision prompts

Body:

The current rate-limit dialog (and similar decision prompts) is a blocking TUI modal.
This causes three compounding problems during active coding sessions:

1. Harness freeze: Background tasks (e.g. run_in_background watchers) cannot deliver

their completion signals while the modal is open. This breaks automation patterns like
auto-resuming after a 5h window reset.

1. Context obscured: The modal overlays the in-progress work. Users must scroll up to

read the full task context before making a meaningful choice.

1. Poor readability for rich choices: Development decisions often involve multi-line

descriptions, code snippets, and option rationale. A modal with limited space and no
markdown rendering makes these hard to read and impossible to copy.

Proposed change:

Add a settings.json key to let users choose how prompts are delivered:

{
"promptStyle": "chat"
}

┌─────────┬──────────────────────────────────────────────────────────────────────────┐
│ Value │ Behavior │
├─────────┼──────────────────────────────────────────────────────────────────────────┤
│ "modal" │ Current behavior (blocking TUI dialog). Default to preserve backwards │
│ │ compatibility. │
├─────────┼──────────────────────────────────────────────────────────────────────────┤
│ │ Deliver the prompt as a regular message in the conversation stream. │
│ "chat" │ Harness stays live; background tasks keep running; user replies in chat │
│ │ as normal. │
└─────────┴──────────────────────────────────────────────────────────────────────────┘

A settings.json option like "rateLimitAction": "wait" to silently default to waiting
(without even a chat prompt) would also address the full automation case.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.159
• Feedback ID: b50ac897-d0df-4428-921f-4da1d2c122d8

Errors

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