fix(supervisor-middleware): configure HTTP/2 keepalive on middleware gRPC channel

[letv1nnn]

Summary

The middleware gRPC channel was the only long-lived client in the repo without HTTP/2 keepalive config. Without it, idle connections are silently reaped by intermediaries and dead peers go undetected until the next evaluation attempt.

This is a prerequisite for #2428 (WebSocket middleware), where long-lived bidirectional streams make a stale connection session-fatal rather than a single-retry inconvenience.

Related Issue

#2474

Changes

• Added http2_keep_alive_interval, keep_alive_while_idle, keep_alive_timeout, and http2_adaptive_window to the Endpoint builder in crates/openshell-supervisor-middleware/src/remote.rs. The configuration is the same as in the crates/openshell-core/src/grpc_client.rs gRPC channel builder.

Testing

• mise run pre-commit passes
• Unit tests added/updated
• E2E tests added/updated (if applicable)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (if applicable)

[copy-pr-bot]

This pull request requires additional validation before any workflows can run on NVIDIA's runners.

Pull request vetters can view their responsibilities here.

Contributors can view more details about this message here.

[pimlock]

/ok to test dc3b339

[pimlock]

Thanks for picking this up. One small nit and this should be good to go.

[pimlock]

/ok to test 5c87d01