Clarify list_vault path parameter to prevent model confusion

Models kept passing the vault name as both vault_name AND path
(e.g. vault_name='obsidian-skt', path='obsidian-skt'), producing garbage
results. The old description 'Relative path within the vault' was too
vague — models interpreted path as the vault identifier.

- path: now explicitly says 'NOT the vault name — that's vault_name'
- Added concrete Usage section with 4 examples
- Described as 'Subfolder inside the vault' not 'Relative path'

server.py

@@ -164,13 +164,21 @@ def list_vault(
 
     Args:
         vault_name: Name of the vault (subdirectory name under vaults root)
-        path: Relative path within the vault. Empty string = vault root.
+        path: Subfolder inside the vault. Omit or pass "" for vault root.
+            NOT the vault name — that's vault_name. Examples:
+            "" or omit = vault root, "NPCs" = vault/NPCs/, "NPCs/Hostile" = deeper.
         recursive: If True, list all nested contents recursively.
         include_files: Include files in results (default True).
         include_directories: Include directories in results (default True).
         file_extensions: Optional filter — only return files with these extensions
             (e.g. ['.md', '.canvas']). Case-insensitive.
 
+    Usage:
+        list_vault("obsidian-skt")              → root listing
+        list_vault("obsidian-skt", "")          → same, explicit
+        list_vault("obsidian-skt", "NPCs")       → subfolder
+        list_vault("obsidian-skt", "", True)     → recursive from root
+
     Returns:
         directories: list of subdirectory info dicts
         files: list of file info dicts (name, path, type, size, modified)