feat(web): write descriptions and comments with a visual editor

ts-rich-editor (TipTap) shows the formatting while writing: bold,
italic, strike, code, headings, lists, task lists, quotes, code blocks
and links, with @ suggesting the project's members and pasted
screenshots uploaded as attachments. It reads and writes the same
Markdown the API keeps (mentions as @[Name](id), images as
attachment:<id>, tables too), so nothing already written changes.

Used for comments, replies, editing a comment or a description, a new
ticket from the board and the public proposal form; the Markdown hint
and the paste directive are gone. List markers sat on a line of their
own, and task lists showed a stray bullet, in the editor and when read.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/10-futuro.md

@@ -64,3 +64,4 @@ Mucho trabajo para lo que aportan hoy; se pueden recuperar si alguien los necesi
   `taskstream: true` en un `PATCH`.
 - Paquete inicial de la web de 2,13 MB a 1,88 MB con `@pi/ui` 0.0.4, que ya no registra Chart.js al importarse ni
   depende de `lodash`.
+- Descripciones y comentarios con editor visual (guardado en Markdown), con menciones y capturas pegadas.