Add option to hide session name bar in TUI

Feature Request

When a session is named (via --resume <name> or /rename), Claude Code displays a prominent colored bar above the input field showing the session name. There is currently no way to hide this bar.

Problem

The session name bar takes up vertical space and is visually intrusive, especially when running multiple panes in a terminal multiplexer or split-pane setup. The session name is already propagated to the terminal title via escape sequences (OSC 0/2), so the information is available in the tab/window title without the inline bar.

Proposed Solution

Add a setting (e.g., in ~/.claude/settings.json or as an environment variable) to control whether the session name bar is rendered inline in the TUI. Something like:

{
  "showSessionNameBar": false
}

When disabled, the session name would still be propagated to the terminal title via escape sequences, but the inline bar above the input field would be hidden.

Context

• The session name already appears in the terminal tab/window title, so hiding the bar doesn't lose information
• Users with split-pane setups or smaller terminal windows want to maximize usable space
• This bar appears to be a recent addition with no opt-out