Rm client proxy cache flag

[matthewlouisbrockman]

Resolves the feature flag for disabling local cache by letting the caller pass it in. API retains it, client proxy loses it.

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Note

Medium Risk
Medium risk because it changes runtime caching behavior for sandbox routing lookups (potential latency increase on client proxies and different cache consistency characteristics), and removes a feature-flag fallback path.

Overview
This PR removes the SandboxCatalogLocalCacheFlag and instead makes Redis sandbox catalog local caching an explicit useLocalCache constructor parameter, with client-proxy now constructing the catalog with caching disabled while the API orchestrator keeps caching enabled. The Redis catalog implementation is updated to treat the cache as optional (nil) and the unit test is rewritten to assert behavior with caching enabled vs disabled without relying on feature-flag targeting.

^{Written by Cursor Bugbot for commit f40d8ed. This will update automatically on new commits. Configure here.}

[cursor]

PR Summary

Medium Risk
Medium risk because it changes sandbox routing lookup caching behavior and the NewRedisSandboxesCatalog API, which could impact request latency or cache lifecycle if callers don’t enable/close the cache correctly.

Overview
Makes the Redis-backed sandbox catalog’s local read-through cache explicitly opt-in via a ReadThroughCache() constructor option, removing the LaunchDarkly flag (sandbox-catalog-local-cache) and related feature-flag plumbing. client-proxy now uses the Redis catalog without a local cache, while the API orchestrator explicitly enables the cache; tests are updated to cover cached vs non-cached behavior and the catalog now guards cache operations when caching is disabled.

^{Written by Cursor Bugbot for commit 8f3ff83. This will update automatically on new commits. Configure here.}