fix(REN-4): use mathematical angle brackets U+27E8/U+27E9 in delimiter table

[kostub]

Summary

Fixes REN-4 from issues.md: the delimiter table in +[MTMathAtomFactory delimiters] mapped \langle, \rangle, <, and > to the deprecated CJK angle brackets U+2329/U+232A, while the symbol (open/close) table already mapped them to the correct mathematical angle brackets U+27E8/U+27E9. This caused:

• \langle x \rangle and \left\langle x \right\rangle to render with different glyphs.
• \left\langle…\right\rangle and all \big*\langle forms to be unable to grow, because all 8 bundled fonts only ship growable vertical variants for uni27E8/uni27E9 — not uni2329/uni232A.

Changes:

• iosMath/lib/MTMathAtomFactory.m: change all four delimiter-table entries (<, >, langle, rangle) from U+2329/U+232A to U+27E8/U+27E9.
• iosMathTests/MTMathListBuilderTest.m: update two existing fixtures whose expected boundary nuclei were the old (deprecated) code points. Serialization assertions (\left< x\right> , \Biggm<) are unchanged because </> remain the shortest inverse commands for U+27E8/U+27E9.
• Add regression test testAngleBracketDelimiterConsistency that directly encodes the invariant: both the symbol-table path (\langle x \rangle) and the delimiter-table path (\left\langle x \right\rangle, \left< x \right>) must produce U+27E8/U+27E9 nuclei.

Test plan

• Verified RED: new regression test fails before the production fix (6 assertion failures, all 〈/〉 vs ⟨/⟩).
• Verified GREEN: all 293 tests pass after the fix.
• swift build succeeds cleanly.
• Serialization round-trip preserved: \left< x\right> and \Biggm< unchanged.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request updates the angle bracket delimiters (<, >, \langle, \rangle) to use the mathematical Unicode characters U+27E8 and U+27E9 instead of the deprecated U+2329 and U+232A characters, and adds a new test to ensure delimiter consistency. The feedback suggests using uppercase hex digits for the Unicode escape sequence in the test file to maintain consistency with the rest of the codebase.

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[gemini-code-assist]

For consistency with the rest of the codebase (including line 500 in this file and MTMathAtomFactory.m), please use uppercase hex digits for the Unicode escape sequence (\u27E8 instead of \u27e8).

        @[ @"\\Biggm\\langle", @(kMTMathAtomRelation),@(kMTDelimiterSize4), @"\u27E8", @"\\Biggm<" ],

[kostub]

EM-REVIEW v1

Severity: NON-BLOCKING. No blocking issues found. Independently sanity-checked the diff via gh pr diff 232.

Summary

REN-4 fix is correct and complete. The four delimiter-table entries in iosMath/lib/MTMathAtomFactory.m (<, >, langle, rangle) move from the deprecated CJK angle brackets U+2329/U+232A to the mathematical angle brackets U+27E8 ⟨ / U+27E9 ⟩, so the delimiter table now agrees with the symbol table.

Verified findings

• Codepoints correct: U+27E8 (⟨ left), U+27E9 (⟩ right).
• All four delimiter-table entries updated; delimiter and symbol tables now agree. No remaining U+2329/U+232A references in the changed entries.
• Reverse-map delimValueToName round-trip stays safe: < remains the shortest command for U+27E8, so serialization fixtures (\left< x\right>) are unchanged.
• New regression test testAngleBracketDelimiterConsistency is meaningful: it exercises both the symbol-table path (\langle x \rangle) and the delimiter-table path (\left\langle, \left<), asserts identical nuclei (U+27E8/U+27E9), and asserts the serialization round-trip stays \left< x\right>.
• Two stale fixtures updated correctly (MTMathListBuilderTest.m lines ~500 and ~1719).
• Prior pass reports 293 tests pass.

Minor nit (non-blocking)

• The fixture at line ~1719 uses lowercase ⟨ while the rest of the diff uses uppercase ⟨. Functionally identical; cosmetic only.

No approval, no merge — review comment only.