fix(experiments): reject reused PCAP page receipt IDs

Check page receipt uniqueness at the SDK workflow boundary before recording observations. A duplicate-ID injection over real MCP succeeds before the fix and fails after it without writing an answer; an unmodified real reply remains valid. Keep original measurements and production defaults unchanged.

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>
Co-authored-by: Kaoru0822 <208281322+kaoru0822-kitauji@users.noreply.github.com>

experiments/analysis-efficiency/measure.mjs

@@ -588,6 +588,8 @@ const inspectPcapTarget = async () => {
         "PCAP page identity, scope or coverage differs from its parent",
       );
     uris = page.page.items;
+    if (observations.some((item) => item.evidence_id === selected.evidence_id))
+      throw new Error("PCAP retained read reused an Evidence identity");
     observations.push(pcapObservation(selected));
   } else {
     const {

experiments/analysis-efficiency/pcap-small-captures.md

@@ -146,6 +146,13 @@ injection setup loaded the separate CommonJS client and did not inject a fault;
 that discarded setup attempt remains private alongside the corrected ESM runs.
 Original measured driver sources, token totals and timing data remain unchanged.
 
+The driver also requires a distinct Evidence receipt for the retained URI page.
+A private SDK consumer injection reuses the summary's response ID after a real
+MCP reply: the preceding driver accepts it, the corrected driver rejects it
+without writing an answer, and an unmodified real reply still passes. This
+checks receipt uniqueness before recording observations; it does not establish
+that a provider actually returned duplicate IDs.
+
 **Decision: keep existing complete defaults; add no production optimization.**
 For these compact recordings and this question, summary/page costs more total
 input in both real-model pairs. No stable speed or CPU/memory benefit justifies