scrum_review: switch curl to stdin so large diffs don't blow argv

Phase 4-bundle review (128KB diff) hit "Argument list too long" when
curl --data was passed the body as a literal arg. Pipe via stdin
with --data-binary @- instead. Lifts the practical bundle size from
~30KB to whatever fits in process memory.

Caught while running the harness scrum on golangLAKEHOUSE today —
the bigger Phase A+B harness diff (4566 lines) tripped it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/scrum_review.sh

@@ -81,10 +81,14 @@ $DIFF_CONTENT
   printf "  %-6s %s ... " "$short" "$model"
   local t0=$SECONDS
   local status
-  status=$(curl -sS -o /tmp/scrum_resp.json -w '%{http_code}' --max-time 240 \
+  # Pipe the body via stdin (`-d @-`) — large diffs (>~128KB) blow
+  # past the kernel's argv limit when passed via `--data <literal>`.
+  # Phase A+B was 128875 bytes and hit "Argument list too long" until
+  # this fix.
+  status=$(printf '%s' "$body" | curl -sS -o /tmp/scrum_resp.json -w '%{http_code}' --max-time 240 \
     -X POST "$GATEWAY/v1/chat" \
     -H 'Content-Type: application/json' \
-    --data "$body")
+    --data-binary @-)
   local elapsed=$((SECONDS - t0))
   if [ "$status" != "200" ]; then
     printf "✗ HTTP %s (%ds)\n" "$status" "$elapsed"