feat(tui): removed cursor positioning and refactored TUI rendering with explicit env defaults

- Removed getCursorPosition() method from Component interface and implementations, eliminating hardware cursor positioning support.
- Changed PI_HARDWARE_CURSOR environment variable default from implicit true to explicit '1' with fallback pattern.
- Changed PI_CLEAR_ON_SHRINK environment variable default from implicit false to explicit '0' with fallback pattern.
- Added screen clearing on TUI startup to prevent shell prompts from bleeding into first rendered frame.
- Refactored full-render logic into reusable fullRender() helper function.

packages/tui/src/utils.ts

@@ -5,6 +5,13 @@ export { Ellipsis, extractSegments, sliceWithWidth, truncateToWidth, wrapTextWit
 // Pre-allocated space buffer for padding
 const SPACE_BUFFER = " ".repeat(512);
 
+/*
+ * Replace tabs with 3 spaces for consistent rendering.
+ */
+export function replaceTabs(text: string): string {
+	return text.replaceAll("\t", "   ");
+}
+
 /**
  * Returns a string of n spaces. Uses a pre-allocated buffer for efficiency.
  */