problems tab, plain words for latex errors, a readable log

[swimmingbrain]

Errors, warnings and the log were the weakest part of the editor: raw TeX messages, no idea which file they came from, and a log that was a wall of text.

What changed

• One Problems tab instead of Errors and Warnings. Every problem is a card: a headline in plain words, what it means, what to try, file and line, and the source line as TeX read it with a bar where it stopped. Click it and the editor jumps there, opening the file if it has to.
• Notes about margins, stretched lines and substituted fonts are there too, hidden until you switch them on.
• Errors TeX can't place, a missing package for example, are placed by searching the sources.
• Copy one problem or all of them as text that reads well in an issue or a chat. Problems that look like the app's fault rather than the document's get a link that opens a prefilled issue.
• The log tab has colors, line numbers, search, a full/clean toggle, copy and download.
• The status bar counts the problems and opens them on click, and it follows the cursor now instead of only updating on edits.
• The parser is tested against 18 real transcripts from the engine, one per kind of mistake. pnpm test runs with every check.