Fix: default border mutation and head widget title

[mohitr2111]

Problem

1. Shared Layout Mutation: SpaceTimeVisualizerWidget directly modifies the class-level TVBWidget.DEFAULT_BORDER dictionary. This permanently injects a min_width that affects all subsequently instantiated widgets (like HeadWidget or PhasePlaneWidget) for the remainder of the kernel session.

2. HTML Title Rendering: HeadWidget incorrectly renders its raw class object in the HTML title (<class 'tvbwidgets.ui.head_widget.HeadWidget'>) instead of its class name.

3. Kwargs Unpacking Error: HeadWidget.init uses *kwargs in its super() call. This unpacks dictionary keys as positional arguments, throwing a TypeError if any extra keyword arguments are passed.

Fix

1. Layout: Used a shallow copy ({**self.DEFAULT_BORDER}) in SpaceTimeVisualizerWidget to prevent mutating the shared layout dictionary.

2. Title: Appended .name to the HTML string interpolation in HeadWidget to correctly render the title as HeadWidget.

3. Kwargs: Replaced *kwargs with **kwargs in HeadWidget.init to properly pass keyword arguments.

Files changed

• tvbwidgets/ui/spacetime_widget.py — 1 line
• tvbwidgets/ui/head_widget.py — 2 characters

Test plan

1. Added 1 regression test in tvbwidgets/tests/test_spacetime_widget.py to ensure layouts aren't mutated.

2. Added 2 regression tests in tvbwidgets/tests/test_head_widget.py to verify title rendering and kwarg initialization.