feat(mode): enabled conditional transcript compaction logic

- Introduced conditional scrollback clearing during UI renders when transcript compaction is enabled.
- Updated `CommandController` and `EventController` to respect the `display.collapseCompacted` setting.
- Configured `SelectorController` to trigger a chat rebuild and UI reset when the compaction setting changes.
- Updated `InteractiveMode` to dynamically toggle between collapsed and full inline history based on user settings.

packages/coding-agent/src/modes/controllers/command-controller.ts

@@ -1200,7 +1200,15 @@ export class CommandController {
 			this.ctx.rebuildChatFromMessages();
 
 			this.ctx.statusLine.invalidate();
-			this.ctx.ui.requestRender();
+			// Same as the auto-compaction rebuild: a collapsed transcript is an
+			// intentional replacement, so drop the stale pre-compaction scrollback
+			// instead of repainting the shrunken frame below it. With collapse
+			// disabled the full history stays inline and scrollback is kept.
+			if (this.ctx.settings.get("display.collapseCompacted")) {
+				this.ctx.ui.requestRender(true, { clearScrollback: true });
+			} else {
+				this.ctx.ui.requestRender();
+			}
 		} catch (error) {
 			if (error instanceof CompactionCancelledError) {
 				outcome = "cancelled";