feat(spaces): docs-kind spaces render as pure documentation repos

Adds a `kind` column to spaces ('project' default, 'docs' for Wiki).
Docs spaces skip projects/tasks fetches and render only the page tree.
Sidebar caret for docs spaces expands to top-level pages (#/page/:id).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/db/repos/spaces.js

@@ -30,7 +30,7 @@ export async function list() {
 
 export async function update(id, patch, actor) {
   const before = await getById(id);
-  const fields = ['name','description','theme','slug'];
+  const fields = ['name','description','theme','slug','kind'];
   const sets = [], vals = [];
   let i = 1;
   for (const f of fields) {