Improve public surface summary and caveats

Adds a concise public-surface summary block with intended use, non-use caveats, and evidence-first wording. Existing README content is preserved below the block.

README.md

@@ -12,6 +12,18 @@ tags:
   - evidence-surface
 ---
 
+<!-- cjc0013-public-surface-note:start -->
+## Public Surface Summary
+
+Public-data review surface for nuclear/UAP-adjacent context, designed for inspection and triage rather than object identification.
+
+Use this for: public-data inspection and triage around nuclear/UAP-adjacent context.
+
+Do not use this as: object identification, extraordinary-claim validation, or claims without public-source caveats.
+
+Caveat discipline: context aid; not identification claim; public-source caveats.
+<!-- cjc0013-public-surface-note:end -->
+
 # Nuclear UAP Evidence Surface
 
 This Space is a simple public viewer for a reduced, hashed analytical dataset about one specific question: