Allow setting custom inference timeout

[pentschev]

Summary

Makes the inference routing timeout configurable via openshell inference set --timeout <secs> and openshell inference update --timeout <secs>, replacing the hardcoded 60-second default. Timeout changes propagate dynamically to running sandboxes within the route refresh interval (~5 seconds) without requiring sandbox recreation.

The timeout was observed running OpenCode for a complex build task on a DGX Spark running nemotron-3-super:120b via Ollama, this feature allows longer running tasks to succeed.

Related Issue

Closes #641

Changes

• Add timeout_secs field to ClusterInferenceConfig, SetClusterInferenceRequest, SetClusterInferenceResponse, GetClusterInferenceResponse, and ResolvedRoute proto messages
• Add timeout field (Duration) to the router's ResolvedRoute struct with a DEFAULT_ROUTE_TIMEOUT of 60 seconds
• Remove the global reqwest::Client timeout; apply per-request .timeout(route.timeout) in backend.rs
• Thread timeout_secs through server persistence (upsert_cluster_inference_route, build_cluster_inference_config, bundle resolution)
• Map proto timeout_secs to router ResolvedRoute.timeout in the sandbox's bundle_to_resolved_routes()
• Include timeout_secs in the bundle revision hash so timeout changes trigger route cache refreshes in running sandboxes
• Add --timeout CLI flag to inference set (default 0 = 60s) and inference update (optional)
• Update docs/inference/configure.md with timeout usage and hot-reload behavior
• Update architecture/inference-routing.md with per-request timeout semantics, proto field additions, and CLI surface

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)

[github-actions]

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[pentschev]

I have read the DCO document and I hereby sign the DCO.