* fix(shell): volume.balance no longer drains all volumes onto one server
The density-based capacity function reads per-disk VolumeInfos sizes, but
adjustAfterMove only updated VolumeCount and the selectedVolumes map. The
planner re-read a stale topology after every move, so the source node's
density never dropped and it kept moving volumes until that node was empty.
Move the volume's size accounting between disks after each planned move so the
density recomputes and the loop converges to an even distribution.
* refactor(shell): O(1) volume removal and direct disk lookup in adjustAfterMove
removeVolumeInfo swaps with the last element instead of shifting, and the disk
is fetched by key rather than ranging the DiskInfos map.
* fix(shell): correct volume.list -writable filter unit and comparison
* fix(shell): correct volume.list -writable filter unit and comparison
* chore(shell): fix typo in EC shard helper param names
* fix(shell): use exact match for volume.balance -racks/-nodes filter
The old strings.Contains-based filter quietly included any id that was a
substring of the user-supplied flag value (e.g. -racks=rack10 also matched
rack1). Replace it with an exact-match set parsed from the comma-separated
flag value, and add regression tests for both -racks and -nodes paths.
Also fix a small typo in the "remote storage" error returned by
maybeMoveOneVolume.
* fix(shell): use exact match for volume.balance -racks/-nodes filter
The old strings.Contains-based filter quietly included any id that was a
substring of the user-supplied flag value (e.g. -racks=rack10 also matched
rack1). Replace it with an exact-match set parsed from the comma-separated
flag value, and add regression tests for both -racks and -nodes paths.
Also fix a small typo in the "remote storage" error returned by
maybeMoveOneVolume.
* refactor(shell): drop nil sentinel in splitCSVSet, use len() in callers
Chris Lu