chore: gitignore local JOSS review-prep scratch notes

Keeps .joss-review-notes/ (reviewer-by-name prep strategy for
JOSS #10604) local only — must never be published to this public
repo, which the assigned reviewers actively watch.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: brycewang-stanford

.gitignore

@@ -199,3 +199,7 @@ CausalAgentBench/
 
 # Temp files
 MORNING_REPORT_2026-04-29.md
+
+# Local JOSS review-prep scratch (reviewer-by-name strategy notes; never publish
+# to this public repo — the JOSS reviewers actively watch it). Keep local only.
+.joss-review-notes/