feat(gui): Implement on-demand definition lookup with clickable navigation and collapsing

src/mcp_client.py

@@ -384,6 +384,32 @@ def _get_symbol_node(tree: ast.AST, name: str) -> Optional[ast.AST]:
   current = found
  return current
 
+def py_get_symbol_info(path: str, name: str) -> tuple[str, int] | str:
+ """
+    Returns (source_code, line_number) for a specific class, function, or method definition.
+    If not found, returns an error string.
+    """
+ p, err = _resolve_and_check(path)
+ if err:
+  return err
+ assert p is not None
+ if not p.exists():
+  return f"ERROR: file not found: {path}"
+ if not p.is_file():
+  return f"ERROR: not a file: {path}"
+ try:
+  code = p.read_text(encoding="utf-8").lstrip(chr(0xFEFF))
+  lines = code.splitlines(keepends=True)
+  tree = ast.parse(code)
+  node = _get_symbol_node(tree, name)
+  if node:
+   start = cast(int, getattr(node, "lineno"))
+   end = cast(int, getattr(node, "end_lineno"))
+   return ("".join(lines[start-1:end]), start)
+  return f"ERROR: definition '{name}' not found in {path}"
+ except Exception as e:
+  return f"ERROR retrieving definition '{name}' from '{path}': {e}"
+
 def py_get_definition(path: str, name: str) -> str:
  """
     Returns the source code for a specific class, function, or method definition.