Add deterministic public buyer demo proof path

[matt-dean-git]

Summary

• Cherry-pick the deterministic public /sandbox#golden-path proof path onto main without the stacked SEO branch history.
• Route homepage and /protect proof CTAs to the deterministic allow/deny/budget/revoke/Evidence Pack flow.
• Surface receipt IDs in the Evidence Pack viewer.
• Update demo IA regression to require /sandbox#golden-path.
• Preserve caveat: budget-before-upstream is response-shape proof only, not keyed upstream counter/log-delta proof.

Verification

• npm ci
• npm run build
• npm run test:demo-ia
• strict touched-file claim/copy hygiene scan
• git diff --check

Authorization / caveats

• Wayne authorized GO for merge/deploy candidate for the public demo path.
• Wayne explicitly set NO-GO for production promotion.
• Public satgate.io verification is required after merge/deploy.
• This PR is not a production-readiness or production-promotion claim.

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Project	Deployment	Actions	Updated (UTC)
satgate	Ready	Preview, Comment	Jun 27, 2026 6:45pm