[FEATURE] AskUserQuestion: Allow customizing the "Other" option placeholder text

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When using the AskUserQuestion tool, an "Other" option is automatically appended to allow users to provide freeform input. This option displays the hardcoded placeholder text "Type something", which cannot be customized.

Proposed Solution

Add an optional otherPlaceholder parameter (or similar) to the AskUserQuestion tool schema that allows customizing the placeholder text for the "Other" option.

{
  "questions": [{
    "question": "Which file should I modify?",
    "header": "File",
    "options": [
      {"label": "config.json", "description": "Main configuration"},
      {"label": "settings.yaml", "description": "User settings"}
    ],
    "multiSelect": false,
    "otherPlaceholder": "Enter custom file path..."
  }]
}

Alternative Solutions

• Adding guidance in the question text itself (e.g., "Select Other to enter a custom path...") - works but is verbose and less elegant
• Not using AskUserQuestion and relying on natural conversation - loses the structured UX benefits

Priority

Medium - Would be very helpful

Feature Category

Interactive mode (TUI)

Use Case Example

This is limiting when building plugins or skills where the freeform input has a specific purpose. For example:

• A file path input might benefit from "Enter file path..."
• A search query might use "Describe what you're looking for..."
• A custom command might show "Enter command arguments..."

Additional Context

This would improve the UX for plugin developers building interactive workflows where freeform input has specific semantics.