feat(ui): add Ctrl/Cmd+L to send selected text to chat

Bind mod+l to append the current selection into the chat composer
(Cursor-style), and move session sidebar toggle to mod+alt+l so desktop
menus stay in sync. Closes #208.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/lib/addSelectionToChat.ts

@@ -0,0 +1,153 @@
+import { EditorView } from '@codemirror/view';
+import { focusChatInput } from '@/components/chat/composer/editor/dom';
+import {
+  formatCodeSelectionMarkdown,
+  rangeToMarkdown,
+  trimSelectionValue,
+  wrapMarkdownSelectionForChat,
+} from '@/components/chat/message/selectionMarkdown';
+import { useInputStore } from '@/sync/input-store';
+import { useUIStore } from '@/stores/useUIStore';
+
+const CHAT_INPUT_HOST_SELECTOR = '[data-chat-input="true"]';
+
+const isInsideChatComposer = (node: Node | null): boolean => {
+  if (!node) {
+    return false;
+  }
+  const asElement = node as Element;
+  const element = typeof asElement.closest === 'function'
+    ? asElement
+    : (node as Node).parentElement;
+  return Boolean(element?.closest(CHAT_INPUT_HOST_SELECTOR));
+};
+
+const readTextControlSelection = (element: Element): string | null => {
+  if (isInsideChatComposer(element)) {
+    return null;
+  }
+
+  const tag = element.tagName?.toLowerCase();
+  if (tag === 'textarea') {
+    const control = element as HTMLTextAreaElement;
+    return trimSelectionValue(
+      control.value.slice(control.selectionStart ?? 0, control.selectionEnd ?? 0),
+    ) || null;
+  }
+
+  if (tag === 'input') {
+    const control = element as HTMLInputElement;
+    const type = control.type?.toLowerCase() ?? 'text';
+    if (!['text', 'search', 'url', 'tel', 'password'].includes(type)) {
+      return null;
+    }
+    return trimSelectionValue(
+      control.value.slice(control.selectionStart ?? 0, control.selectionEnd ?? 0),
+    ) || null;
+  }
+
+  return null;
+};
+
+const captureActiveElementSelection = (): string | null => {
+  if (typeof document === 'undefined') {
+    return null;
+  }
+
+  const activeElement = document.activeElement;
+  if (!activeElement || typeof (activeElement as Element).tagName !== 'string') {
+    return null;
+  }
+
+  const text = readTextControlSelection(activeElement as Element);
+  return text ? wrapMarkdownSelectionForChat(text) : null;
+};
+
+const captureCodeMirrorSelection = (): string | null => {
+  if (typeof document === 'undefined') {
+    return null;
+  }
+
+  const focusedEditor = document.querySelector<HTMLElement>('.cm-editor.cm-focused');
+  if (!focusedEditor || isInsideChatComposer(focusedEditor)) {
+    return null;
+  }
+
+  const view = EditorView.findFromDOM(focusedEditor);
+  if (!view) {
+    return null;
+  }
+
+  const { from, to } = view.state.selection.main;
+  if (from === to) {
+    return null;
+  }
+
+  const text = trimSelectionValue(view.state.sliceDoc(from, to));
+  if (!text) {
+    return null;
+  }
+
+  view.dispatch({
+    selection: { anchor: to },
+  });
+
+  return formatCodeSelectionMarkdown(text);
+};
+
+const captureDomSelection = (): string | null => {
+  if (typeof window === 'undefined') {
+    return null;
+  }
+
+  const selection = window.getSelection();
+  if (!selection || selection.rangeCount === 0 || selection.isCollapsed) {
+    return null;
+  }
+
+  const range = selection.getRangeAt(0);
+  if (isInsideChatComposer(range.commonAncestorContainer)) {
+    return null;
+  }
+
+  const plainText = trimSelectionValue(selection.toString());
+  if (!plainText) {
+    return null;
+  }
+
+  const markdown = rangeToMarkdown(range, plainText);
+  selection.removeAllRanges();
+  return wrapMarkdownSelectionForChat(markdown);
+};
+
+/**
+ * Capture the current non-composer selection as chat-ready markdown.
+ * Returns null when nothing usable is selected.
+ */
+export const captureSelectionMarkdownForChat = (): string | null => {
+  return captureCodeMirrorSelection()
+    ?? captureActiveElementSelection()
+    ?? captureDomSelection();
+};
+
+/**
+ * Append the current selection to the chat composer.
+ * When nothing is selected, focuses the chat input (Cursor-style Ctrl/Cmd+L).
+ * Returns true when selected text was appended.
+ */
+export const addSelectionToChat = (): boolean => {
+  const markdown = captureSelectionMarkdownForChat();
+
+  useUIStore.getState().setActiveMainTab('chat');
+  useUIStore.getState().setSessionSwitcherOpen(false);
+
+  if (markdown) {
+    useInputStore.getState().setPendingInputText(markdown, 'append');
+  }
+
+  queueMicrotask(() => {
+    focusChatInput();
+  });
+
+  return markdown !== null;
+};