Defer CM6 mount to onMount so the host is attached when EditorView reads it

After externalising CM6, Obsidian's flavour of EditorView crashed in
its constructor with "Cannot read properties of null (reading
'CSSStyleSheet')" — it dereferences `parent.ownerDocument.defaultView`
during style mounting, and Solid's `ref={...}` callback fires before
the element is appended to the document, so defaultView was null.

Move the mountComposer call from a ref callback into onMount and
capture the host element through a separate ref assignment. The host
is in the document by the time onMount runs, so EditorView's style
mounting finds a real window. Also fixes the "failed to open" notice
that came from the failed view construction.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/components/UserInput.tsx

@@ -4,6 +4,7 @@ import {
     createSignal,
     createEffect,
     onCleanup,
+    onMount,
     useContext,
     Show,
 } from "solid-js";
@@ -55,9 +56,17 @@ export const UserInput: Component<UserInputProps> = ({
     const [composer, setComposer] = createSignal<ComposerHandle | null>(null);
     const [isModalOpen, setIsModalOpen] = createSignal(false);
 
-    const mountInto = (parent: HTMLDivElement) => {
+    let composerHost: HTMLDivElement | undefined;
+
+    // The mount runs in onMount (not in ref={...}) so the host element is
+    // actually attached to the document by the time CM6 reads
+    // `parent.ownerDocument.defaultView` — Obsidian's flavour of EditorView
+    // dereferences `defaultView.CSSStyleSheet`, and Solid's refs fire before
+    // mount, so a synchronous EditorView construction crashes there.
+    onMount(() => {
+        if (!composerHost) return;
         const handle = mountComposer({
-            parent,
+            parent: composerHost,
             placeholder: hasModels()
                 ? "Type your message..."
                 : "No models available",
@@ -87,10 +96,8 @@ export const UserInput: Component<UserInputProps> = ({
             handle.destroy();
         });
 
-        // Defer focus until after the mount finishes so CM6's selection is
-        // ready to receive it.
-        queueMicrotask(() => handle.focus());
-    };
+        handle.focus();
+    });
 
     /**
      * Detects `[[` and `#` typing and opens the Obsidian suggestion modal,
@@ -213,7 +220,12 @@ export const UserInput: Component<UserInputProps> = ({
 
     return (
         <div class="coi-user-input">
-            <div class="coi-composer" ref={mountInto} />
+            <div
+                class="coi-composer"
+                ref={(el) => {
+                    composerHost = el;
+                }}
+            />
             <div class="coi-user-input-options">
                 <ModelSelector
                     selectedModel={currentModel}