why

Update docs to describe new caching workflow

what changed

test plan

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Summary by cubic

Updates the docs to reflect that server-side caching for Browserbase projects is now opt-in instead of on by default.

• V3 and V4 guides and API references now explain that caching is off until a project requests it via Browserbase support.
• The cache/serverCache options still work, but only after project-level enabling; cacheStatus is undefined when disabled.