v1.3.15

This release reshapes the beginner CFOP F2L solver so its output mirrors how the first two layers are actually taught, not just a correct but cryptic move sequence.

Changes:

• Beginner F2L now emits intuitive, learner-style procedures. Each pair is routed to a front working slot (front-right or front-left, reached by a cube rotation) and solved with the recognisable "set up → hide to the back → re-pair → insert" shape. White-corner-up, white-on-side, already-paired, and stuck-piece cases each follow their own clear path, and F is reserved for genuinely extracting a trapped piece.
• More cases now resolve in the side-family trigger vocabulary a beginner recognises, instead of dense search-found chains.
• No public API changes — same beginner: true option on the CFOP solver, just better solutions.

Internal: the standalone permutation cross-check was retired in favour of the Vitest suite (294 tests), now the single pre-merge gate.