perf(obsidian): optimize folder tree for large vaults

The previous implementation read ALL file contents to get frontmatter
when browsing notes, which caused massive slowdown for large vaults
(13k+ files = 13k+ HTTP requests).

Changes:
- Add listAllNotePaths() function that only gets file paths (fast)
- Build folder tree from paths only, no content reading
- Lazy load file content only when user clicks on a file
- Change message from "Loading all notes" to "Loading file list"
- Add logging to show file count being displayed

Performance improvement:
- Before: O(n) HTTP requests where n = number of files
- After: O(1) - just the recursive directory scan
- File content loaded on-demand (1 request per clicked file)

This makes the folder tree instant even for vaults with 10k+ files.

modules/ui/obsidian-notes-editor.js

@@ -300,16 +300,19 @@ async function promptCreateNewNote(elementId, elementType, coordinates) {
     };
 
     const showBrowse = async () => {
-      resultsDiv.innerHTML = "<p>Loading all notes...</p>";
+      resultsDiv.innerHTML = "<p>Loading file list...</p>";
 
       try {
-        const allNotes = await ObsidianBridge.listAllNotes();
+        // Use fast path-only listing (doesn't read file contents)
+        const allNotes = await ObsidianBridge.listAllNotePaths();
 
         if (allNotes.length === 0) {
           resultsDiv.innerHTML = "<p style='color: #999;'>No notes in vault</p>";
           return;
         }
 
+        INFO && console.log(`Displaying ${allNotes.length} notes in folder tree`);
+
         // Build folder tree
         const tree = buildFolderTree(allNotes);
         resultsDiv.innerHTML = renderFolderTree(tree, allNotes);
@@ -321,12 +324,15 @@ async function promptCreateNewNote(elementId, elementType, coordinates) {
             $("#alert").dialog("close");
             try {
               const note = allNotes[index];
+              // Read the file content only when clicked
               const content = await ObsidianBridge.getNote(note.path);
+              const {frontmatter} = ObsidianBridge.parseFrontmatter(content);
+
               resolve({
                 path: note.path,
                 name: note.name,
                 content,
-                frontmatter: note.frontmatter
+                frontmatter
               });
             } catch (error) {
               reject(error);