[Bug]: Agent TUI redraws can block remote runtime RPCs #14331

Operating system

Linux

Orca version

1.4.180

Details

Short summary:

Agent TUI redraws can make the remote runtime stop answering RPCs while TCP remains healthy.

What happened?

A Linux remote runtime repeatedly appeared offline and reconnected. During an affected session:

• ping and TCP connections to the runtime succeeded continuously
• orca status timed out repeatedly
• Electron's main process used one full core
• a CPU profile attributed 86.8% of samples to retained terminal-row finalization

The observed redraw row contained about 4,001 internal spaces followed by status text. The finalizer used /[ \t]+$/g to remove trailing whitespace. When internal whitespace is followed by text, this end-anchored regex repeatedly rescans the run before rejecting it.

How can we reproduce it?

1. Run an agent TUI that redraws a status line about 36 times per second.
2. Emit a retained partial row containing about 4,000 spaces followed by text.
3. Process each redraw through retained terminal-tail finalization.
4. Observe Electron main-process CPU and runtime RPC latency.

Additional evidence:

• observed row arrays contained only four or nine rows, ruling out tail-array size as the cause
• replacing the regex with the existing backward scanner changed a follow-up profile to 99.1% idle
• status calls recovered from repeated approximately 73-second timeouts to 0.23–0.34 seconds in the affected session
• output behavior remained unchanged