Expose channel resiliency tuning in ClientBuilder

[rawkode]

Problem

ClientBuilder does not expose transport-level resiliency controls for long-lived streams.

Impact

Production workloads cannot tune keepalive behavior for their environment, which can lead to dropped connections and delayed failure detection.

Proposed change

• Add ClientBuilder options for channel resiliency tuning, including:
  • keepalive enable/disable semantics,
  • HTTP/2 keepalive interval,
  • HTTP/2 keepalive timeout,
  • TCP keepalive.
• Define sensible defaults for production use.
• Document each option and defaults in API docs/README.
• Add tests that verify builder wiring into channel configuration.

Acceptance criteria

• ClientBuilder exposes the above resiliency settings.
• Defaults are documented and applied when options are omitted.
• Configuration values are reflected in constructed client/channel settings.
• Tests cover option propagation and default fallback behavior.