feat(tui,coding-agent): add OSC 9;4 terminal progress indicators

Emit OSC 9;4 progress start/end sequences during agent streaming and
compaction so terminals (iTerm2, WezTerm, Windows Terminal, Kitty, etc.)
show activity in their tab bar.

Made with love for @lucasmeijer

packages/coding-agent/test/edit-tool-no-full-redraw.test.ts

@@ -27,6 +27,7 @@ class FakeTerminal implements Terminal {
 	clearFromCursor(): void {}
 	clearScreen(): void {}
 	setTitle(_title: string): void {}
+	setProgress(_active: boolean): void {}
 
 	get fullClearCount(): number {
 		return this.writes.filter((write) => write.includes("\x1b[2J\x1b[H\x1b[3J")).length;