[v0.1] Envoy ExtProc integration for llm-d gateway

[rootfs]

Acceptance

• ExtProc header/body mutation consistent with LLM-d filter chains
• Example Envoy configs for common patterns (e.g., A/B test, canary routing)

[Gregory-Pereira]

/assign

[srampal]

Hey @Gregory-Pereira I am already working on this as part of the parent issue 39 which is assigned to me (and 2 others). Let's co-ordinate

[srampal]

/assign

[Gregory-Pereira]

Sanjeev and I discussed this, he will be taking over the issue