Apply OpenType MATH italic correction at run boundaries

[Happypig375]

Summary

• apply the actual glyph/font OpenType MATH italic correction when a slanted math run ends before an upright glyph or delimiter
• preserve same-style Ordinary fusion and attach internal slanted-to-upright corrections to the corresponding fused glyph
• retain text-mode shaping, Rule 16 spacing, scripts, wrappers, composites, and public InnerDisplay mutability semantics
• cache the ink-aware advance only for completed Typesetter-owned inner layouts, avoiding repeated recursive ink-tree traversal
• formalize and enforce the math glyph lookup contract of one glyph per Unicode scalar

The behavior follows the OpenType MATH rule that the last glyph's italic correction is added when a slanted run is followed by a straight character: https://learn.microsoft.com/en-us/typography/opentype/spec/math#mathitalicscorrectioninfo-table

Validation

• Core suite: 1,658/1,658 passed
• Rendering suite (serial): 1,298/1,298 passed
• TestMeasure: 64/64 passed
• exact Issue32MatrixRightDelimiter Skia golden: passed
• negative non-scalar-aligned glyph-provider contract test: passed
• git diff --check: passed
• final senior correctness/performance review: approved
• BenchmarkDotNet AllConstantValues: 572.205 ms mean (failed PR run: 29.294 s; local pre-fix warmup: 35.4 s; prior baseline: about 608 ms)
• BenchmarkDotNet QuarticSolutions: 131.028 ms mean (failed PR run: 344.7 ms; prior baseline: 122.4 ms)

Stack

This is intentionally based on port-iosmath-2026 / #264 because it builds on that port's math-run font-fusion semantics. The final performance repair is bcca7142.

Fixes #32