feat(cli): add DENO_CACHE_MAX_SIZE env var for automatic cache trimming
When set (e.g. DENO_CACHE_MAX_SIZE=2G), automatically trims the cache
directory after cache-writing operations by removing oldest files first
until the cache is under the specified limit. Useful for CI environments
and constrained disk scenarios.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>