chore: v2.8.12 — clone queue and progress, session defaults, chat agents, drops as @ mentions

Whole tree from parallel sessions, plus the version bump:
- Clone: a queue with live progress (Add workspace and extra folders),
  clones run under nice/ionice so the machine stays responsive.
- Settings → AI tools → Session defaults: a new session's default
  permission mode / bypass per account.
- Chat lists the background subagents that have not reported back yet.
- A file pasted or dropped into a claude pane goes in as an @ mention.
- Changes panel: say why amend/undo is refused on a pushed commit.
- openapi.yaml regenerated (Artifacts, Host, resumeById).

client/src/components/ContextMenu.tsx

@@ -165,12 +165,15 @@ export function MenuItem({
   danger,
   disabled,
   testId,
+  title,
   children,
 }: {
   onSelect: () => void;
   danger?: boolean;
   disabled?: boolean;
   testId?: string;
+  /** Hover text — e.g. why a disabled item cannot run. */
+  title?: string;
   children: ReactNode;
 }) {
   return (
@@ -179,6 +182,7 @@ export function MenuItem({
       role="menuitem"
       data-testid={testId}
       disabled={disabled}
+      title={title}
       className={`${MENU_ITEM}${danger ? " !text-status-danger" : ""}`}
       onClick={onSelect}
     >