bug: non-Latin font insert crashes when regular_fonts has fewer than 3 entries

[yunanwg]

Description

When using a non-Latin language (zh, ja, ko, ru) with a regular_fonts configuration that has fewer than 3 entries, compilation crashes with an array index out of bounds error.

This affects both CV and cover letter modules in the current 3.2.0 release.

Reproduction

1. In metadata.toml, set:

[layout.fonts]
    regular_fonts = ["Source Sans 3"]  # only 1 font

2. Compile with a non-Latin language:

typst compile template/cv.typ --input language=zh

3. Error:

error: array index out of bounds (index: 2, len: 1)
   ┌─ src/lib.typ:46:4
   │
46 │     fonts.insert(2, nonLatinFont)
   │     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Root Cause

In src/lib.typ, both cv() (line 46) and letter() (line 134) use fonts.insert(2, non-latin-font) which assumes the font array has at least 2 elements. When overwrite-fonts() returns a user-defined regular_fonts with only 1 entry, the insert at index 2 is out of bounds.

The default _latin-font-list in styles.typ has 3 fonts so it works by default — but any user customization with fewer fonts will crash.

Suggested Fix

Use fonts.push(non-latin-font) or fonts.insert(calc.min(2, fonts.len()), non-latin-font) to handle arrays of any length.

Affected Versions

• 3.2.0 (current release)
• Also present in the cover letter modernization work (Cover Letter improvement - proposal #96 / RFC: Cover letter module modernization (#96) #164)

Affected Files

• src/lib.typ — cv() function (line 46) and letter() function (line 134)