standardize cupy integration

Bump version to 0.1.1

Co-Authored-By: Claude <noreply@anthropic.com>

v0.0.1

Document the masterIndex star-estimation mode in README and CLAUDE.md

README: add a "Register toward a master image" usage section describing
masterIndex (default zero-mean all-pairs O(N^2); masterIndex=k pins image k at
the identity and switches to the O(N) star graph) and its noise-robustness
trade-off. Clarify the default gauge in the code-comment block.

CLAUDE.md: rewrite the Estimation section to cover both the all-pairs/zero-mean
mode and the star/fix-node mode (O(N^2) vs O(N) estimation, the pairs= filter
mechanism, the star+fix-node exactness, the trade-off), note the (min,max) edge
keying preserves the sign convention, and correct the gauge-equivalence note --
params_master != params_zm - params_zm[master] once the master run uses a
different pairwise measurement set (now true for coTranslate2d too, not just
coSimilarityTransform2d).

Co-Authored-By: Claude <noreply@anthropic.com>