fix(coding-agent): expand paste markers in Ctrl+Q follow-ups

InputController.handleFollowUp read raw editor text via getText(),
bypassing the paste-store expansion the Enter path applies through
Editor.getExpandedText(). A large paste collapsed into a [Paste #N, +X
lines] marker was therefore sent verbatim to the model when queued with
Ctrl+Q / Ctrl+Enter, silently dropping the pasted content.

Switch the follow-up path to getExpandedText() so queued submissions
match the Enter path. Image markers are untouched; pendingImages
forwarding is unchanged.

Updated existing input-controller stubs (skill-queue, followup-image,
keybindings) to implement getExpandedText, matching the production
CustomEditor surface.

Fixes #3737

packages/coding-agent/test/input-controller-skill-queue.test.ts

@@ -27,6 +27,7 @@ import { TempDir } from "@oh-my-pi/pi-utils";
 type StubEditor = {
 	setText: (text: string) => void;
 	getText: () => string;
+	getExpandedText: () => string;
 	clearDraft: (historyText?: string) => void;
 	addToHistory: Mock<(...args: unknown[]) => unknown>;
 	onSubmit?: (text: string) => Promise<void>;
@@ -67,6 +68,9 @@ function createStubInputControllerContext(opts: {
 		getText() {
 			return editorText;
 		},
+		getExpandedText() {
+			return editorText;
+		},
 		clearDraft(historyText?: string) {
 			if (historyText !== undefined) this.addToHistory(historyText);
 			this.setText("");