tether 0.1.0b5

Added

• tether add LOCATOR --kind KIND (and Repo.add(None, ...)) takes the key
  from the locator's last segment, less the store suffix, for file, icechunk,
  lance, delta and git objects. Other kinds still need a key.
• status, snapshot and verify take KEY..., and diff a repeatable
  --key: an exact key or a prefix ending in / (zarr/). Only those
  objects are contacted and reported. In Python it is keys= on each
  method, and Repo.select_keys, which promote and restore now use too.
  Repo.restore([]) is refused rather than resetting every object;
  keys=None asks for all of them.
• commit KEY... and pull --key KEY commit only those objects, as git commit PATH does. Other manifests and uncommitted .tether/ edits stay
  out of the commit, and objects sharing a branch space are named together.
  A saved plan records its selection under its digest.

Fixed

• secrets.toml adds to a table tether.toml also sets, instead of
  replacing it: a committed Iceberg catalog keeps its type and
  warehouse when secrets.toml adds the catalog's uri, and a committed
  storage_options.region survives a secrets file that adds an endpoint. A
  [uris."..."] or [objects."..."] entry adds to the kind's tables the same
  way, and an Iceberg locator's catalog adds to the kind's.
• file, delta and lance: a region given in more than one place
  (secrets.toml, the locator, storage_options under any spelling) reaches
  the store once, the most specific winning; obstore refused it as a
  duplicate. Icechunk's store checks also honour a locator region.
• Object keys with spaces, parentheses or [ reach jj and git quoted: jj
  rejected such a path as a revset, and git read [ab] as a pattern that
  could sweep another object's manifest into a commit.