M7e: add regression test that Scene recall does not dirty the document

[Rowee13]

Summary

Add a regression test that pins the M7e "recall a Scene does not dirty the document" invariant. The behavior is implemented correctly today, but no test guards it — a future change could silently route recall through the command stack (or add a stray dirty call) without any test failing.

Found during the M7e (v0.2.5) final whole-branch review. Non-blocking.

Detail

Recalling a Scene (MainWindow._on_recall_view) applies tag visibility + render style instantly and tweens only the camera; it deliberately does NOT go through CommandStack and does NOT mark the document dirty (a view change is not a document edit). The final review verified this holds concretely, but tests/test_main_window_scenes.py has no assertion for it.

Suggested test

In tests/test_main_window_scenes.py, add something like:

def test_recall_does_not_dirty_document(qtbot):
    win = _make_window(qtbot)
    win._on_create_view()
    vid = win._model.views.views()[0].id
    win._doc_controller.mark_clean()          # start from a clean state
    undo_before = win._command_stack.can_undo
    win._on_recall_view(vid)
    assert win._doc_controller.dirty is False  # recall must not dirty
    assert win._command_stack.can_undo == undo_before  # recall must not touch the stack
    win._view_animator.cancel()

(Adjust to the actual DocumentController / CommandStack API names.)

Context

• Milestone: M7e (Scenes / saved views), shipped v0.2.5.
• Design: docs/2026-07-22-M7e-scenes-design.md.