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/panePaste.ts

@@ -14,9 +14,10 @@
  * terminal moves the unsent prompt across (`takeRunInput` reads the TUI's
  * input box off the screen and empties it; the chat's draft is pasted back
  * without Enter), so the half-typed text is never left behind on the other side.
- * Attached images' paths go after the text, each in a paste of its own: `claude`
- * turns a paste that is only an image's path into `[Image #n]`, but left a
- * Windows path (`C:\…\drops\…png`) inside a paste of text as a plain path.
+ * Attached images' paths go after the text, each in a paste of its own — how
+ * `codex` attaches one; a `claude` pane gets every file as an `@` mention in
+ * the text instead (`promptForPane`), since a pasted path stayed a plain
+ * `C:\…\drops\…png` there on Windows.
  * The Chat view also answers a menu the CLI asks with (`parsePaneMenu` reads
  * it off the screen; `chooseRunOption`/`answerRunMenu` press its digit, the
  * arrows and Enter, or type into its "Type something" row).