fix(tui): add vertical scrolling to Editor when content exceeds terminal height

The Editor component now accepts TUI as the first constructor parameter,
enabling it to query terminal dimensions. When content exceeds available
height, the editor scrolls vertically keeping the cursor visible.

Features:
- Max editor height is 30% of terminal rows (minimum 5 lines)
- Page Up/Down keys scroll by page size
- Scroll indicators show lines above/below: ─── ↑ 5 more ───

Breaking change: Editor constructor signature changed from
  new Editor(theme)
to
  new Editor(tui, theme)

fixes #732

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Breaking Changes
+
+- Extensions using `Editor` directly must now pass `TUI` as the first constructor argument: `new Editor(tui, theme)`. The `tui` parameter is available in extension factory functions. ([#732](https://github.com/badlogic/pi-mono/issues/732))
+
 ### Added
 
 - New `input` event in extension system for intercepting, transforming, or handling user input before the agent processes it. Supports three result types: `continue` (pass through), `transform` (modify text/images), `handled` (respond without LLM). Handlers chain transforms and short-circuit on handled. ([#761](https://github.com/badlogic/pi-mono/pull/761) by [@nicobailon](https://github.com/nicobailon))
@@ -13,6 +17,7 @@
 
 ### Fixed
 
+- Editor no longer corrupts terminal display when loading large prompts via `setEditorText`. Content now scrolls vertically with indicators showing lines above/below the viewport. ([#732](https://github.com/badlogic/pi-mono/issues/732))
 - Piped stdin now works correctly: `echo foo | pi` is equivalent to `pi -p foo`. When stdin is piped, print mode is automatically enabled since interactive mode requires a TTY ([#708](https://github.com/badlogic/pi-mono/issues/708))
 - Session tree now preserves branch connectors and indentation when filters hide intermediate entries so descendants attach to the nearest visible ancestor and sibling branches align. Fixed in both TUI and HTML export ([#739](https://github.com/badlogic/pi-mono/pull/739) by [@w-winter](https://github.com/w-winter))
 - Added `upstream connect`, `connection refused`, and `reset before headers` patterns to auto-retry error detection ([#733](https://github.com/badlogic/pi-mono/issues/733))