fix(qa): checkpoint receipts print the report link for their exploration file

qa-functional-webhook-report failed in two of three censuses because the
report linked .qa-evidence/NNN capture folders as "checkpoints" and never
linked exploration-NNN.json. The checkpoint receipt now prints
link: [checkpoint NNN](exploration-NNN.json), and the functional report
template says capture folders are not checkpoints.

qa/templates/functional-report-template.md

@@ -33,6 +33,7 @@ evidence and regression baselines. Do not combine their scores or outcomes.
 ## Discoveries and permanent tests
 
 Link each `exploration-NNN.json` checkpoint, saved before its next probe, in this report.
+Each checkpoint receipt prints its `link`; `.qa-evidence/NNN` capture folders are not checkpoints.
 Use one Markdown entry per checkpoint, for example:
 
 - [checkpoint 001](exploration-001.json) — how this observation shaped the next probe.