feat(tui): LaTeX environments, text, and command support for math rendering

[SparkofSpike]

Summary

Extend the existing LaTeX math rendering with full environment-block support, common inline commands, accent commands, command-aware subscripts/superscripts, and case-insensitive environment matching.

Changes

• Environment rendering: New render_environment() dispatcher and try_render_env() integration detecting begin{aligned/pmatrix/bmatrix/vmatrix/Bmatrix/cases/array/smallmatrix). Two-pass column-width alignment. Opening/closing brackets on their own lines for multi-row.

• Cases: Unicode brace extension chars (U+23A7/U+23A8/U+23A9). Trailing commas stripped from left cells.

• Array: Parse column spec {c|c|l|r} with vertical bar separators.

• Multi-line env auto-newline: Envs start on fresh line. Fixed: out.trim() -> trim_end() so leading newline survives final trim.

• Case-insensitive env names: to_ascii_lowercase() matching.

• Text/operatorname: Render braced arg as plain text.

• Left/right/big brackets: Consume size modifiers, output bracket.

• Font commands: mathbf/mathrm/mathit/mathsf/textbf/textrm/textit, recursively render.

• Accent commands: hat/bar/tilde/dot/ddot/vec/breve/check/acute/grave with Unicode combining marks.

• Spacing: quad(4)/qquad(8)/thinspace/semicolon(2)/!(skip). Fixed: backslash-comma now renders as space.

• Fraction aliases: dfrac/tfrac/cfrac dispatch to frac.

• Binomial: binom{n}{k} renders as (n/k).

• Command-aware sub/superscripts: _mu/_nu/^dagger/^rho reads full command. Extended Unicode superscript letters a-z.

• Underbrace/Overbrace/Phantom: Passthrough rendered content. Phantom no-op.

• Substack: Renders as-is.

• Styled symbols: Extended mathcal{A-Z} and mathbb{set}.

• Extended symbol table: 80+ new symbols.

• Markdown code span preservation: Split by backticks.

• Currency/escape protection: Rejects $ followed by digit; detects backslash-$.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change
• Documentation update
• Refactoring (no functional changes)
• Tests

Testing

• cargo check --workspace --all-features --locked (0 errors, 0 warnings)
• cargo fmt --all -- --check
• cargo test --workspace --all-features --locked
• Manual testing: incremental check after each edit; existing tests pass

Checklist

• Updated docs or comments as needed
• Added or updated tests where relevant
• Verified TUI behavior manually if UI changes
• Harvested/co-authored credit uses a GitHub numeric noreply address

Related Issues

No-Issue: Continues from #4957 (feature request), #4974 (previous foundation). Adds environment blocks and inline command support on top of the existing math rendering.

Notice

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