Merge PR #2950: feat(coding-agent): add copy affordance to completed /btw answers (@wolfiesch)

Adds 'c copy' to the completed /btw panel footer (alongside b branch / Esc
dismiss), copying the sanitized visible answer to the clipboard. The copy
shortcut is guarded by canCopyBtw + main-editor focus + empty editor.

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

@@ -99,6 +99,7 @@ export class InputController {
 	#enhancedPaste?: EnhancedPasteController;
 	#focusedLeftTapListenerInstalled = false;
 	#btwBranchListenerInstalled = false;
+	#btwCopyListenerInstalled = false;
 	// Tap counter for the double-← gesture; reset whenever a quiet gap
 	// (>= LEFT_DOUBLE_TAP_MAX_GAP_MS) starts a fresh sequence. See
 	// #detectLeftDoubleTap.
@@ -174,6 +175,17 @@ export class InputController {
 				return { consume: true };
 			});
 		}
+		if (!this.#btwCopyListenerInstalled) {
+			this.#btwCopyListenerInstalled = true;
+			this.ctx.ui.addInputListener(data => {
+				if (!matchesKey(data, "c")) return undefined;
+				if (!this.ctx.canCopyBtw()) return undefined;
+				if (this.ctx.ui.getFocused() !== this.ctx.editor) return undefined;
+				if (this.ctx.editor.getText().trim()) return undefined;
+				void this.ctx.handleBtwCopyKey();
+				return { consume: true };
+			});
+		}
 		this.ctx.editor.onEscape = () => {
 			// Active context maintenance owns Esc: auto/manual compaction,
 			// handoff generation, and auto-retry backoff all advertise