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

@@ -9,6 +9,18 @@ pinned: false
 license: cc-by-4.0
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+<!-- cjc0013-public-surface-note:start -->
+## Public Surface Summary
+
+Interactive public-record review surface for senator wealth/trading context, built to keep provenance, caveats, and review status visible.
+
+Use this for: reviewing public-record wealth/trading context with provenance, caveats, and inspection status visible.
+
+Do not use this as: investment advice, allegations, or claims detached from source-level caveats.
+
+Caveat discipline: public-record review aid; not investment advice; source caveats before claims.
+<!-- cjc0013-public-surface-note:end -->
+
 # Senate Disclosure Reader
 
 Plain-English reader for official Senate financial disclosures: search filers, reported wealth ranges, transaction rows, filing dates, and source receipts.