[FEATURE]: TUI - Dialog boxes have inconsistent horizontal padding and need vertical centering improvements (UI) #12948

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Describe the enhancement you want to request

Problem
The TUI dialog system currently exhibits visual inconsistencies:

1. Inconsistent Padding: Base components use 4 units of horizontal padding, while custom implementations (Status, Help, Connect) use 2 units, creating a disjointed look.
2. Vertical Off-Center: Dialogs are hardcoded to render at 25% from the top (height / 4), rather than being truly centered in the viewport.

Proposed Solution

1. Standardize Padding:
   Update dialog-status.tsx, dialog-help.tsx, and dialog-provider.tsx to use paddingLeft={4} paddingRight={4} to match the base DialogSelect component.

2. Fix Vertical Centering:
   In ui/dialog.tsx, remove the manual padding calculation and rely on flexbox for perfect centering.

   // ui/dialog.tsx
   // Remove: paddingTop={dimensions().height / 4}
   // Add:
   justifyContent="center"

This ensures all dialogs (/models, /agents, /status, etc.) share the same visual weight and alignment.