feat(notes): [[note]] is an inline link, not bracketed text

Choosing a note from the [[ completion wrote [[Title]] as plain text. It made a
real link behind the scenes — it showed in the panel under the note — but in the
note itself it stayed brackets, and "it doesn't become a link" is exactly how that
reads. A wiki link is a link where it is written.

Now a [[note]] renders inline as the title, in the accent colour, and a click on it
opens the note it points at. It is atomic — contenteditable="false" — so it moves
and deletes as one thing and a click is a click, not a caret landing mid-word. And
it appears the moment it is chosen: the completion drops the finished link in,
brackets and all swallowed, rather than text waiting to become a link when the note
is next opened.

The seam holds both ways: markdownToHtml lifts [[title]] into the link the same way
it already lifts an image, and htmlToMarkdown reads the link back to [[title]] by
the title it carries — so what is on disk is still the same Markdown, and a note
opened, saved and reopened is unchanged.

e2e: choosing a note writes an inline link, it survives the round-trip through
Markdown and a reload, and clicking it opens the note it names. Full suite green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/routes/noter/+page.svelte

@@ -916,6 +916,7 @@
 			<NoteEditor
 				note={selected}
 				notes={notes}
+				onopennote={(title) => openLink({ kind: 'note', target_id: title })}
 				onchange={(body) => {
 					draft = body;
 					typed();