allozaur/feat/chat form contenteditable (#26717)

* feat: Add contenteditable tokenizer for badge/code-chip chat input

* feat: Add source-space undo/redo history for the rich input

* feat: Split text glued to a closing code fence onto its own line

* feat: Add ChatFormContenteditable rich input renderer

* feat : wire the contenteditable into ChatForm with auto-switch gating

tools/ui/tests/client/chat-form-enter-code-block.svelte.test.ts

@@ -0,0 +1,112 @@
+// Guards the Enter-key contract of the chat form against the
+// fenced-code-block flow: while the caret sits inside a fenced
+// block region - closed, or still OPEN while the user is typing
+// one - plain Enter adds a line instead of submitting the message.
+// The textarea path is covered here end-to-end (the contenteditable
+// consumes the same case locally; see chat-form-contenteditable).
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { render } from 'vitest-browser-svelte';
+import { userEvent } from 'vitest/browser';
+import { tick } from 'svelte';
+import { SETTINGS_KEYS } from '$lib/constants/settings-keys';
+import { settingsStore } from '$lib/stores/settings.svelte';
+import ChatFormTestWrapper from './components/ChatFormTestWrapper.svelte';
+
+function textareaIn(container: HTMLElement): HTMLTextAreaElement {
+	const el = container.querySelector('textarea');
+	if (!(el instanceof HTMLTextAreaElement)) throw new Error('textarea not rendered');
+	return el;
+}
+
+describe('ChatForm Enter in code blocks', () => {
+	beforeEach(() => {
+		settingsStore.updateConfig(SETTINGS_KEYS.SEND_ON_ENTER, true);
+	});
+
+	it('adds a line after a still-open fence instead of submitting', async () => {
+		const onSubmit = vi.fn();
+		const { container } = render(ChatFormTestWrapper, { onSubmit });
+		await tick();
+
+		const textarea = textareaIn(container);
+		await userEvent.click(textarea);
+		await userEvent.keyboard('```');
+		await tick();
+
+		await userEvent.keyboard('{Enter}');
+		await tick();
+
+		expect(onSubmit).not.toHaveBeenCalled();
+		expect(textarea.value).toBe('```\n');
+	});
+
+	it('keeps adding lines while the block stays open', async () => {
+		const onSubmit = vi.fn();
+		const { container } = render(ChatFormTestWrapper, { onSubmit });
+		await tick();
+
+		const textarea = textareaIn(container);
+		await userEvent.click(textarea);
+		await userEvent.keyboard('```js');
+		await tick();
+
+		await userEvent.keyboard('{Enter}');
+		await userEvent.keyboard('const a = 1;');
+		await userEvent.keyboard('{Enter}');
+		await tick();
+
+		expect(onSubmit).not.toHaveBeenCalled();
+		expect(textarea.value).toBe('```js\nconst a = 1;\n');
+	});
+
+	it('submits when the caret is before the opening fence', async () => {
+		const onSubmit = vi.fn();
+		const { container } = render(ChatFormTestWrapper, { onSubmit });
+		await tick();
+
+		const textarea = textareaIn(container);
+		await userEvent.click(textarea);
+		await userEvent.keyboard('```');
+		await tick();
+
+		textarea.setSelectionRange(0, 0);
+
+		await userEvent.keyboard('{Enter}');
+		await tick();
+
+		expect(onSubmit).toHaveBeenCalledTimes(1);
+	});
+
+	it('submits on Enter outside a code block', async () => {
+		const onSubmit = vi.fn();
+		const { container } = render(ChatFormTestWrapper, { onSubmit });
+		await tick();
+
+		const textarea = textareaIn(container);
+		await userEvent.click(textarea);
+		await userEvent.keyboard('hello');
+		await tick();
+
+		await userEvent.keyboard('{Enter}');
+		await tick();
+
+		expect(onSubmit).toHaveBeenCalledTimes(1);
+	});
+
+	it('submits on Ctrl+Enter even inside a code block', async () => {
+		const onSubmit = vi.fn();
+		const { container } = render(ChatFormTestWrapper, { onSubmit });
+		await tick();
+
+		const textarea = textareaIn(container);
+		await userEvent.click(textarea);
+		await userEvent.keyboard('```');
+		await tick();
+
+		await userEvent.keyboard('{Control>}{Enter}{/Control}');
+		await tick();
+
+		expect(onSubmit).toHaveBeenCalledTimes(1);
+	});
+});