[Neovim] Fix obsidian note_id_func generating only one random char

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

home-manager/features/neovim/config/lua/plugins/obsidian.lua

@@ -58,9 +58,11 @@ return {
         return title:gsub("[^A-Za-z0-9-_]", ""):lower()
       else
         -- If title is nil, just put the date and four random characters
+        local suffix = ""
         for _ = 1, 4 do
-          return os.date("%Y-%m-%d ") .. string.char(math.random(65, 90))
+          suffix = suffix .. string.char(math.random(65, 90))
         end
+        return os.date("%Y-%m-%d") .. "-" .. suffix
       end
     end,
   },