Evict cached results to keep .barca/ under its size limit

Usage: barca gc [OPTIONS]

Options:
      --max-size <SIZE>  A limit for this run in place of the configured one: 20GB, 500MB, 20GiB, bytes, 10% (of the filesystem) or off (only leftovers and superseded results)
      --dry-run          Preview cached and planned work; execute nothing and record no run
      --json             Emit JSON on stdout (the default when stdout is not a terminal)
      --pretty           Emit human-readable output (the default when stdout is a terminal)
      --env <ENV>        Use a separate cache and history for this environment
  -h, --help             Show concise command help
      --examples         Show all command examples without running anything

Examples:
  barca gc --dry-run              # what would be evicted, per tier, and what it leaves
  barca gc                        # evict now, down to 80% of [cache] max_size
  barca gc --max-size 5GB         # a one-off tighter budget

All examples: barca gc --examples
More: barca docs cache ("Disk use")
