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/coding-agent/src/tools/render-utils.ts

@@ -8,7 +8,7 @@ import * as os from "node:os";
 import { type Ellipsis, truncateToWidth } from "@oh-my-pi/pi-tui";
 import type { Theme } from "../modes/theme/theme";
 
-export { Ellipsis, truncateToWidth } from "@oh-my-pi/pi-tui";
+export { Ellipsis, replaceTabs, truncateToWidth } from "@oh-my-pi/pi-tui";
 
 // =============================================================================
 // Standardized Display Constants
@@ -672,10 +672,6 @@ export function wrapBrackets(text: string, theme: Theme): string {
 	return `${theme.format.bracketLeft}${text}${theme.format.bracketRight}`;
 }
 
-export function replaceTabs(text: string): string {
-	return text.replace(/\t/g, "   ");
-}
-
 function pluralize(label: string, count: number): string {
 	if (count === 1) return label;
 	if (/(?:ch|sh|s|x|z)$/i.test(label)) return `${label}es`;