Stagehand docs say server-side caching is now opt-in for Browserbase projects

The stagehand-python 4.4.1a0.dev1700 prerelease updates the documentation to reflect that server-side caching for Browserbase projects is no longer on by default. The V3 and V4 guides and API references were changed to explain the new behavior.

Caching stays off until a project requests it through Browserbase support. The cache and serverCache options still work, but only after project-level enabling. When caching is disabled, cacheStatus is undefined.

Agents that expect cached Stagehand responses will not get them until a Browserbase project is explicitly enabled, so cache behavior should not be assumed.

Code that reads cacheStatus should handle undefined, which is the value returned when caching is disabled.

Teams that depend on caching should request project-level enabling through Browserbase support before relying on it.