Curved text: readability and orientation policy

[rowland]

Summary

Separate reader-friendly orientation behavior from raw geometry.

Scope

• Define explicit orientation modes:
  • geometric
  • upright (reader-friendly default)
• Encode the policy that top-of-circle text stays comfortable to read without rotating the page and bottom-of-circle text flips appropriately.
• Define how vertical anchors map when text is on the inner vs outer side of a curve.
• Keep this logic as a policy layer over placement rather than embedding it in low-level trig.

Acceptance Criteria

• Add focused tests for top-arc vs bottom-arc behavior.
• Add tests proving anchor behavior does not invert unexpectedly when readable mode is enabled.
• Document the default orientation policy in API comments or adjacent docs.