Inconsistent TUI padding in the agent pane

[hamza-usmani]

Steps to reproduce

1. Open an agent pane.
2. Compare the padding around different regions of the TUI: transcript, input box, status line, tool-call blocks.

Expected Behavior

Padding is consistent across the pane and matches the rest of the app's spacing.

Actual Behavior

Padding varies between regions of the agent pane TUI.

Padding or alignment on left is inconsistent across different boxes and regions here.

Proposed fix

Design polish pass.

Related: #518 Agent Pane UX umbrella.