Fix rotation and stack text edge cases

[eigger]

Summary

• Rotate the element-level dither protection mask with the final image.
• Measure stack child padding independently per axis, using coerced and wrapped text fields.
• Preserve rotated text bounds while avoiding oversized square temporary layers.
• Add regression coverage for rotation, long text, numeric template strings, and null defaults.

Review and verification

• Fresh Sol 6.1 review: no remaining findings.
• 1725 tests passed locally.
• Ruff lint/format, mypy, and diff checks passed.