fix(config): unwrap {nuwiki:{...}} wrapper in apply_change

workspace/didChangeConfiguration settings from Neovim arrive as
{ "nuwiki": { "wiki_root": ..., "wikis": [...] } } because
server_settings() in lua/nuwiki/lsp.lua wraps the payload in a
"nuwiki" namespace key.  apply_change() was trying to deserialise that
outer object directly as InitOptions, which always succeeded but produced
all-None fields (unknown keys are ignored by serde), so every settings
refresh was silently dropped.

Unwrap single-key objects whose value is also an object before
deserialising — this handles the Neovim wrapper while keeping the flat
VimL shape working unchanged.

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

crates/nuwiki-lsp/src/config.rs

@@ -367,8 +367,21 @@ impl Config {
 
     /// Re-apply settings received via `workspace/didChangeConfiguration`.
     /// On parse failure the existing config is returned unchanged.
+    ///
+    /// Accepts both the flat shape (`{ "wikis": [...] }`) produced by the
+    /// VimL client, **and** the Neovim-style wrapper (`{ "nuwiki": { ... } }`)
+    /// that `server_settings()` in `lua/nuwiki/lsp.lua` produces.  Any other
+    /// single-key object whose value is an object is also unwrapped so
+    /// editors that namespace settings by server name continue to work.
     pub fn apply_change(&mut self, value: &serde_json::Value) {
-        let raw: InitOptions = match serde_json::from_value(value.clone()) {
+        // Unwrap { "nuwiki": { ... } } → { ... } so both clients work.
+        let inner = value
+            .as_object()
+            .and_then(|m| if m.len() == 1 { m.values().next() } else { None })
+            .filter(|v| v.is_object())
+            .unwrap_or(value);
+
+        let raw: InitOptions = match serde_json::from_value(inner.clone()) {
             Ok(r) => r,
             Err(_) => return,
         };