Add DSH to the agent roster and Install > AI

Official npm @deepseek-ai/dsh (bin: dsh) rides the mise path like Dim.
dsh has no TUI, so the interactive launch is the documented 'dsh web'
and one-shot prompts use 'dsh --profile headless'. Auth is dsh-managed,
so it stays out of the AI Hub registry.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019hLK3wsDuKVAC37GgDqg6H

bin/omarchy-agent

@@ -115,6 +115,14 @@ dim)
     command=(dim)
   fi
   ;;
+dsh)
+  # dsh has no TUI: `dsh web` is the interactive form, headless the one-shot
+  if [[ -n ${prompt:-} ]]; then
+    command=(dsh --profile headless "$prompt")
+  else
+    command=(dsh web)
+  fi
+  ;;
 *)
   echo "Unsupported default agent: $agent" >&2
   exit 1