fix(follow-link): create missing page + wrap word on <CR>

Two missing pieces in the previous "follow creates page" fix:

1. **`wiki_root` never reached the server.** The Lua glue (and the
   Vim autoload glue) was sending the config under `settings` — that
   field is for `workspace/didChangeConfiguration` notifications, not
   for `initialize`. The server's `Config::from_init_params` reads
   `initialization_options`, so `wiki_root` arrived as `None`, the
   `Wiki` aggregate was empty, and `wiki_for_uri` returned `None` →
   `resolve_target_uri` bailed before reaching my synthesise path,
   leaving `<CR>` with "No Location Found".

   Both glues now send the same payload under both keys:
   - `lua/nuwiki/lsp.lua` → adds `init_options = init_options()`
     alongside the existing `settings = …`.
   - `autoload/nuwiki/lsp.vim` → adds `initialization_options` to
     the `lsp#register_server` call.

   The server keeps reading from `initializationOptions` at startup
   *and* honouring `didChangeConfiguration` later (Phase 11 plumbing).

2. **No-wiki fallback in the server.** Even with the glue fix above,
   users who launch nuwiki on an ad-hoc `.wiki` file outside any
   workspace folder would still get an empty `wikis` list. The
   `LinkKind::Wiki` arm now falls back to a new
   `synthesise_page_uri_next_to(source_uri, path)` which builds the
   future page next to the current file. `<CR>` on `[[NewPage]]`
   opens `./NewPage.wiki`, save creates it.

3. **`<CR>` on a plain word now wraps + follows.** Mirrors vimwiki's
   `:VimwikiFollowLink`: when the cursor isn't already inside
   `[[…]]`, the new `nuwiki.commands.follow_link_or_create` /
   `nuwiki#commands#follow_link_or_create` first wraps the word
   under cursor as `[[word]]`, places the cursor inside the link,
   then dispatches `vim.lsp.buf.definition()` /
   `:LspDefinition`. Both editor paths now bind `<CR>` /
   `<S-CR>` / `<C-CR>` / `<C-S-CR>` to this smart variant.

Verified end-to-end:
- `[[NewPage]]` with the rebuilt binary: definition returns
  `file:///tmp/wiki/NewPage.wiki` as a Location, so the editor
  opens an empty buffer for it.
- A bare `MyPage` word becomes `[[MyPage]]` in the buffer before
  the follow request fires.

Total 381 tests still pass; fmt + clippy clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ftplugin/vimwiki.vim

@@ -122,10 +122,10 @@ if !has('nvim')
     nnoremap <silent><buffer> <Leader>w<Leader>i  :call nuwiki#commands#diary_generate_index()<CR>
 
     " Links
-    nnoremap <silent><buffer> <CR>       :LspDefinition<CR>
-    nnoremap <silent><buffer> <S-CR>     :split<CR>:LspDefinition<CR>
-    nnoremap <silent><buffer> <C-CR>     :vsplit<CR>:LspDefinition<CR>
-    nnoremap <silent><buffer> <C-S-CR>   :tabnew<CR>:LspDefinition<CR>
+    nnoremap <silent><buffer> <CR>       :call nuwiki#commands#follow_link_or_create()<CR>
+    nnoremap <silent><buffer> <S-CR>     :split<CR>:call nuwiki#commands#follow_link_or_create()<CR>
+    nnoremap <silent><buffer> <C-CR>     :vsplit<CR>:call nuwiki#commands#follow_link_or_create()<CR>
+    nnoremap <silent><buffer> <C-S-CR>   :tabnew<CR>:call nuwiki#commands#follow_link_or_create()<CR>
     nnoremap <silent><buffer> <BS>       <C-o>
     nnoremap <silent><buffer> <Tab>      /\[\[<CR>:nohlsearch<CR>
     nnoremap <silent><buffer> <S-Tab>    ?\[\[<CR>:nohlsearch<CR>