Feature request: pin input line and attached UI elements to the bottom of the terminal window

Currently, as context grows and the chat scrolls, the command input line and the panels attached to it (for example, the active plan shown above the input) move up together with the rest of the content. This makes it hard to keep track of the current plan or context status without manually scrolling back down.

Request

Pin the following elements to the bottom of the terminal window:

• The command/input line.
• Anything directly attached above it (e.g., the active plan, current step, or context status).
• Anything directly attached below it (e.g., hint text, keybindings, or mode indicators).

The main conversation/context area should scroll above this fixed bottom region, similar to how most modern chat clients and terminal multiplexers behave.

Example layout

┌─────────────────────────────────────┐
│ [scrollable conversation/context]   │
│                                     │
│ ...                                 │
│                                     │
├─────────────────────────────────────┤  ← fixed separator
│ context: 66.8% (175.1k/262.1k)      │
│ Plan: implement auth middleware     │
│   Step 3 of 5: write tests          │
├─────────────────────────────────────┤
│ > _                                 │  ← input line always here
├─────────────────────────────────────┤
│ Ctrl+S submit · /help · /plan       │
└─────────────────────────────────────┘

Why this helps

• The current plan and context status remain visible at all times.
• Users always know where to type without chasing the input line.
• Less vertical scrolling during long agent turns.

Optional setting

A TOML option such as tui.toml:

[tui]
fixed_input_region = true

would let users keep the current behavior if they prefer it.

No files or tests are named. Start by locating the terminal UI entry point that renders the conversation, input line, and attached panels, then trace the current scrolling and layout behavior. Done means the input region stays at the bottom while the conversation scrolls above it, with the optional setting preserving current behavior if implemented.