fix(scene): report whether animation mutations record undo history

[knoxHuang]

📌 Background

Successful animation operations do not always push an animation-scoped Undo entry. Without the scene-process outcome, a following Undo or Redo can be routed as though a new history entry exists and consume older history.

✨ Changes

• Return whether a successful animation operation recorded Undo history.
• Set undoRecorded only when the animation clip snapshot changes and an Undo command is pushed.
• Cover both history-producing and no-history operation outcomes.

💡 Design Notes

The scene process is the source of truth for Undo history creation. Consumers use the explicit outcome instead of inferring it from operation success.

🧪 QA Steps

N/A — this is a Cocos CLI scene-process contract. Product validation is performed through the PinK Animation Editor integration flow.

⚠️ Risks

• The focused Jest suite could not start in this worktree because jest is not installed; source test execution remains pending in a dependency-complete CLI checkout.

[knoxHuang]

Merged into #822 as 6436ea4.