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/lib/promptAttach.ts

@@ -4,8 +4,9 @@
  * file or folder dragged from the Files panel (`ATTACH_MIME`, read back by
  * `PromptEditor`'s drop) or from a Chat pane's activity panel
  * (`dragAttachments`, `dragSkill`: a skill becomes the prompt's `/command`) and the files uploaded through a prompt box in the
- * last day (`recentUploads`, kept in this browser). An attachment is a path
- * sent with the prompt, so nothing here touches the server.
+ * last day (`recentUploads`, kept in this browser), and `claudeMention`, the
+ * `@` form a file is handed to `claude` in. An attachment is a path sent with
+ * the prompt, so nothing here touches the server.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -101,6 +102,19 @@ export function droppedText(
   }
 }
 
+/** An attached file as Claude Code's `@` mention, which `claude` reads at
+ *  submit — an image as an image — whether it came on the command line or in
+ *  a paste. A bare pasted PATH becomes `[Image #n]` only when the TUI catches
+ *  the paste on its own and finishes before Enter: on Windows (psmux) it
+ *  stayed a plain `C:\…\drops\…png` in the prompt, and on the command line
+ *  a path is never an image at all. A Windows path's backslashes become `/`
+ *  (Windows takes either); a path with a space is quoted. */
+export function claudeMention(path: string): string {
+  if (path.startsWith("@")) return path;
+  const p = /^[A-Za-z]:\\/.test(path) ? path.replace(/\\/g, "/") : path;
+  return /\s/.test(p) ? `@"${p}"` : `@${p}`;
+}
+
 export const SKILL_MIME = "application/x-agenthub-skill";
 // A skill's name as Claude Code types it: `name` or `plugin:name`.
 const SKILL_RE = /^[\w.-]+(?::[\w.-]+)?$/;