Remove stale docs, abandoned plans, and debug workflows

- Delete 5 outdated docs (twitter-nft-plan, zk-github-attestation-plan,
  WORKFLOW_GUIDELINES, generating-proofs, SECURITY_AUDIT_FAUCET)
- Delete docs/examples/ (only referenced from deleted plan doc)
- Delete archive/PLAN_VK_ATTESTATION.md (marked ABANDONED)
- Delete .github/workflows/dump-env.yml (debug experiment)
- Move demo-report.md to notes/ (valuable record, not documentation)
- Add proof artifact patterns to .gitignore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: amiller

.github/workflows/dump-env.yml

@@ -15,6 +15,12 @@ claim-test/
 attestation.json
 certificate.json
 identity-proof/
+bundle.json
+claim.json
+inputs.bin
+inputs.json
+proof.bin
+proof.hex
 browser-container/proof-[0-9]*/
 browser-container/data/
 zk-proof/circuits/proof.json