feat(tidy3d): FXC-5401-default-to-local-caching-true-in-tidy-3-d-2-11

[marcorudolphflex]

Note

Medium Risk
Changes default runtime behavior to persist simulation artifacts locally, which can increase disk usage and expose new cache-related edge cases in environments with restricted filesystems.

Overview
Local simulation caching is now on by default. The default for td.config.local_cache.enabled is flipped from False to True, and docs/changelog are updated to reflect the new opt-out behavior.

This affects new installs and users who never explicitly set the flag, as repeated runs may start writing cache entries to the configured cache directory automatically.

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