For discussion: Add optional hard wrapping on input (editor.hard-wrap)

[gwicke]

For-discussion implementation of #2274. Functional and working well for me, but NOT ready for merge yet. I am looking for feedback first, and there are some documented deferred / backlog items in the temporary design doc. To test, build hx with this patch, and add the following section to your config.toml:

[editor.hard-wrap]
enable = true

---

Implement hard wrap at input time, similar to vim's textwidth: when a non-whitespace character is entered past text-width, the affected line is broken at its softwrap wrap point and continues on the next line with the line's indentation, list marker (aligned under the item content, never a repeated marker) and comment token re-applied. Words are never split; a word too long to fit overflows until a space is entered past it. Only lines being edited are touched, and soft wrapping remains an independent display transform.

The break point is computed by reusing the softwrap traversal (DocumentFormatter) with the width budget reduced on continuation rows for the continuation prefix, so the wrap points match what softwrap would display. The continuation-prefix resolver floors the line's leading whitespace, raises it to the tree-sitter indent when available, then appends the comment token (reusing continue-comments detection) and a list-marker delta. enable and list-markers are resolved per position through the innermost language layer (following injections), then the document language, then the global config. List-marker detection is configurable via the auto-pairs-style [editor.hard-wrap].list-markers option (bool or custom regex).

The wrap applies as a second transaction composing into the same pending changeset as the insert, keeping a single undo step. Paste, completion/snippet inserts and Enter are intentionally unchanged.

See docs/261010_hard_wrap.md for the full design.