Expose M3 upright SE(2) source implementation

[Legender134]

Expose the CPU-only spatialcf/upright_se2@1 implementation for advanced direct General-IR use. It supports world XY translation and own/reference-pivot upright yaw, with independent proof replay and a single general outcome assembler. Incomplete searches remain UNKNOWN or noncertified witnesses.

This is the exact public-source projection of the reviewed development change: five new source modules, supporting retained-owner changes and README/API/concept documentation. Existing generation, CLI behavior and package version remain unchanged.

Validation:

• Exact 155-file projection and import policy verified; the 15-file diff matches the reviewed source change byte for byte.
• Local README/CLI smoke: 37 passed. Wheel/sdist built with existing dependencies; packaging contracts and archive source-byte checks passed.
• Source acceptance: full CPU 4,108 passed / 56 skipped, warning-strict M3 420 passed, compatibility seals and worker determinism gates passed; independent whole-branch review had no findings.