Migrates 3 sites in src/outline_tool.py:
1. L49 (outline body) - the ast.parse SyntaxError handler.
outline() now returns Result[str]. On SyntaxError, the data
is the formatted error string (preserved for backwards-compat
with callers that read the formatted string), and the errors
list has the ErrorInfo.
2. L90 (walk ast.unparse for returns) - was except ...: pass.
Now appends ErrorInfo to enclosing parse_errors list.
3. L109 (walk ast.unparse for ImGui context) - same.
outline() returns Result(data='\n'.join(output), errors=parse_errors).
get_outline() also returns Result[str].
Tests updated to check result.ok and use result.data.
ed