feat: add security testing utilities for mTLS certificate verification

[Ethan-Arrowood]

Summary

• Extracts OCSP and CRL testing utilities from harper's integration test suite into this reusable module
• Adds pure-Node.js X.509 certificate generation (via pkijs + Node.js webcrypto, no openssl CLI), an OCSP responder server, a CRL HTTP server, and high-level setupOcspResponderWithCerts / setupCrlServerWithCerts helpers
• Exports all new APIs from the package root (index.ts) and documents them in the README
• Fixes build configuration: adds explicit rootDir to tsconfig.build.json, adds skipLibCheck for pkijs/asn1js TS6 compatibility, upgrades @types/node to 22.15.21

New exports

// High-level helpers
setupOcspResponderWithCerts(certsPath, hostname?, maxRetries?): Promise<OcspResponderContext>
stopOcspResponder(ctx): Promise<void>
setupCrlServerWithCerts(certsPath, hostname?, maxRetries?): Promise<CrlServerContext>
stopCrlServer(ctx): Promise<void>
startCrlServer(certsPath, port, certs): Promise<CrlServerContext>

// Certificate generation
generateOcspCertificates(outputDir, ocspHost, ocspPort)
generateCrlCertificates(outputDir, crlHost, crlPort)

// Low-level primitives
generateEd25519KeyPair, createCertificate, createCRL, certToPem, crlToPem,
makeCRLDistributionPointsExt, makeOCSPAIAExt, makeExtKeyUsageExt,
signBasicOCSPResponse, startOcspServer, stopOcspServer

Test plan

• All 115 harper integration tests pass (including OCSP and CRL suites) with imports updated to @harperfast/integration-testing
• npm run build succeeds cleanly
• npm run check passes

Next steps

After this PR is merged and released, the extract-integration-testing-framework branch in harper will be updated to consume the released version and remove the now-redundant integrationTests/utils/security/ directory.

🤖 Generated with Claude Code

[kriszyp]

I'm curious about the motivation for this, and why this is deemed generic enough to exist in the integration framework instead of the project testing this? (The PR description doesn't really indicate)

[Ethan-Arrowood]

I assume these utils would be relevant for other projects that may want to do similar security testing. Anything from harper-pro to plugins or applications.