feat: [US-010] improve http.Agent bridge compatibility

[NathanFlurry]

Summary

• branch from the US-009 tip commit 1f2d362e
• improve Node bridge http.Agent compatibility and _http_agent exposure
• add conformance/runtime-driver coverage and regenerate the Node conformance report

Validation

• pnpm --filter @secure-exec/nodejs build
• pnpm --filter @secure-exec/core build
• pnpm --filter @secure-exec/nodejs exec tsc --noEmit -p tsconfig.json
• pnpm --filter @secure-exec/core exec tsc --noEmit -p tsconfig.json
• pnpm vitest run packages/secure-exec/tests/runtime-driver/node/index.test.ts ❌

First concrete failing error from the targeted test run:

• packages/secure-exec/tests/runtime-driver/node/index.test.ts > NodeRuntime > accepts explicit execution factory and keeps driver-owned runtime config
• expected '/' to be '/sandbox-app'

Additional note:

• the four newly added HTTP-agent runtime-driver tests timed out at 5000ms in this run.