Backfill SPDX identifiers and harden catalog frontmatter validation.

Mapped licenses get canonical SPDX ids and missing multi-entry publishers are filled in so CI can reject invalid enums and unknown SPDX values.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: TMHSDigital

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,6 +2,9 @@
 RESEARCH/*
 !RESEARCH/README.md
 
+# Session scratch (follow-up logs, not catalog source of truth)
+_scratch/
+
 # Secrets / local env
 .env
 .env.*