feat(examples): add sundial problem demonstrating core GA operations

[utiberious]

Summary

Adds a sundial example script that demonstrates core geometric algebra operations (rotors, reflections, projections, duals) applied to a practical problem from Russell Goyder's work.

Partially addresses #506 (extracts the core GA verification ideas, not the full cheat sheet).

Changes

• examples/Terminal/sundial.py: New example demonstrating:
  • Rotor construction and sandwich product
  • Reflections via blade sandwich
  • Projections and rejections
  • Dual operation
  • All verified with assertions

Test plan

• Script runs without errors: python examples/Terminal/sundial.py
• Unit tests pass

[utensil]

Thanks for this! Cross-checked against the russellgoyder/sundial repo — the ops here are genuinely core to that analysis. util.rotate uses exactly the same rotor formula (cos(θ/2) - bivec*sin(θ/2) applied as R*M*~R), frame.planet() composes rotors the same way, and the sun_dir calc matches frame.sunray() directly.

Two things:

1. Please remove the comment # Mirrors issue 506 from upstream. (line 14) — internal bookkeeping, not useful to readers.
2. The PR description lists "rejections" but there's no rejection in the code. Either add v - proj_B(v) or remove it from the description.

[utiberious]

Addressed both:

1. Removed the internal bookkeeping comment.
2. Added a rejection example (rej_B(v) = v - proj_B(v)) so the code now matches the PR description.

Pushed in 4c56a15.