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/onboarding/OnboardingWizard.tsx

@@ -29,9 +29,9 @@ import { PetSettings } from "../settings/PetSettings";
 import { Swatch, THEME_LABELS } from "../settings/AppearanceSettings";
 import { markOnboarded, useOnboarding } from "../../lib/userPrefs";
 import {
-  DEFAULT_MODES,
   readDefaultMode,
   readDefaultTool,
+  SAFE_MODES,
   writeDefaultMode,
   writeDefaultTool,
   type DefaultMode,
@@ -310,7 +310,7 @@ function AgentStep() {
               writeDefaultMode(m);
               setMode(m);
             }}
-            options={DEFAULT_MODES.map((m) => ({ value: m, label: t(`agent.modes.${m}`) }))}
+            options={SAFE_MODES.map((m) => ({ value: m, label: t(`agent.modes.${m}`) }))}
           />
         </div>
         <p className="text-xs text-fg-muted">{t("agent.permissionHint")}</p>