fix(dream-cli): double-quote tmpdir in gpu_reassign RETURN trap

_gpu_reassign registered a cleanup trap with single-quoted
outer syntax, so $tmpdir expansion was deferred until fire
time. RETURN traps are process-level (not function-scoped),
so when the function returns to cmd_gpu the trap fires again
in cmd_gpu's scope where $tmpdir is unbound. Under set -u
that triggers 'tmpdir: unbound variable' and exit 1 even
on successful reassign.

Switched to double-quoted outer to bake $tmpdir in at
trap-set time (single-quoted inner keeps paths with spaces
safe). Matches the already-landed pattern at dream-cli:542.

macOS Apple Silicon and AMD paths are unaffected (the
nvidia-smi early-return at line 2825 precedes the trap
registration). Linux NVIDIA and Windows WSL2 + NVIDIA
passthrough are the affected surface.

Author: yasinBursali

dream-server/dream-cli

@@ -2866,7 +2866,7 @@ _gpu_reassign() {
     # Write topology to tmpfile and run assignment
     local tmpdir
     tmpdir=$(mktemp -d)
-    trap 'rm -rf "$tmpdir"' RETURN
+    trap "rm -rf '$tmpdir'" RETURN
     echo "$topo_json" > "$tmpdir/topo.json"
 
     local enabled_services="${ENABLED_SERVICES:-llama_server,whisper,comfyui,embeddings}"