fix: flat vault type resolution — remove type/ prefix from links and protected folders

- Type relationship links: [[type/essay]] → [[essay]] (matches flat vault structure)
- PROTECTED_FOLDERS / KEEP_FOLDERS: only attachments, _themes, assets
- TypeSelector navigation: type/slug → slug
- Updated all 14 affected test files
- All 612 Rust tests + 2151 frontend tests pass

src/components/NoteAutocomplete.test.tsx

@@ -38,7 +38,7 @@ const entries = [
 ]
 
 const personTypeEntry = makeEntry({
-  path: '/vault/type/person.md', filename: 'person.md', title: 'Person',
+  path: '/vault/person.md', filename: 'person.md', title: 'Person',
   isA: 'Type', color: 'yellow', icon: 'user',
 })
 const typeEntryMap: Record<string, VaultEntry> = { Person: personTypeEntry }