feat: let a worker group override the dependency cache object store (#11019)

* feat: let a worker group override the dependency cache object store

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R6hBAWqNUsQMAJ7P59juug

* fix: address review findings on the worker-group cache override

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R6hBAWqNUsQMAJ7P59juug

* fix: close the remaining config read route and re-evaluate the override on plan change

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R6hBAWqNUsQMAJ7P59juug

* fix: serialize override reloads and keep a store a failed rebuild still serves

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R6hBAWqNUsQMAJ7P59juug

* fix: require enterprise for the cache override and lock its whole transition

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R6hBAWqNUsQMAJ7P59juug

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Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>