HTML export panics on multi-byte character after `</` in raw text element

Description

Description

HTML export panics with a char-boundary error when a raw text element (style, script, etc.) contains </ followed by a multi byte character within "tag name length" distance.

Minimal reproduction (typst compile --features html repro.typ repro.html):

#html.elem("style", "</abcd−")

(note the last character is U+2212 MINUS SIGN)

Sorry, can't upload a .typ file, thanks Github!

I get:

thread 'main' panicked at crates/typst-html/src/encode.rs:297:20:
byte index 5 is not a char boundary; it is inside '−' (bytes 4..7) of `abcd−`

The text that triggered this originally is in Typst's standard library documentation for the cbor module: crates/typst-library/src/loading/cbor.rs, line 65, see here. This was observed via tinymist's package doc generator.

Claude patched a local checkout of the typst-html crate, but per CONTRIBUTING.md's policy on AI-implemented contributions I'm only reporting it as an issue rather than opening a PR with Claude's one-line fix.

Operating system: macOS
Typst version: 0.15.1

Operating system

macOS

Typst version

• I am using the latest version of Typst

Start by running the minimal reproduction with the HTML feature, then inspect crates/typst-html/src/encode.rs around line 297 where the char-boundary panic occurs. Compare the raw text example with the triggering text in crates/typst-library/src/loading/cbor.rs around line 65. Done means HTML export completes without panicking when a multi-byte character follows the raw-text terminator prefix.