Sync sanitized implementation and public CI

[faratech]

Summary

• Sync the current implementation from httpjet-internal using its existing public-export allowlist
• Add public fuzzing and interoperability workflows
• Exclude production notes, deployment artifacts, benchmark archives, and private instructions
• Remove production-specific README language

Validation

• Public-export allowlist and credential-pattern checks passed
• Workflow YAML parsing passed
• git diff --check passed
• cargo metadata --no-deps passed

This PR is intentionally not merged yet so it can be refreshed if the ongoing work in httpjet-internal changes the source snapshot.