DocVortex 0.4.18

Changes

• Refactor cross-lane short-tail reattachment in native PDF line layout: candidates are processed once in preceding-line order with a shared _lane_accepts_short_tail predicate, and the source lane participates in the uniqueness check, so a tail accepted by multiple lanes stays in place instead of oscillating between lanes. Spreadsheet projector ordering follows the same stability rule; comprehensive stability and uniqueness tests added.

Full Changelog: v0.4.17...v0.4.18