Improve code-editing guidance in tutorials

[qingqing-ux]

Problem

• Current tutorials rely mainly on Tutorial Copilot text instructions, so users need to infer which code to delete, change, or add from written descriptions.
• For first-time users, text-only guidance is not direct enough and can lead to misunderstanding.
• If Copilot intervenes too heavily, it weakens the experience of completing the tutorial independently.

What Needs Improvement

• Keep Copilot as a behind-the-scenes assistant in tutorials, providing prompts only when users cannot proceed.
• Limit API Reference to the APIs used in the current tutorial.
• Remove drag guidance (code-drag-hint).
• Keep code-editing guidance (code-delete-hint, code-change-hint).
• Compare diffs at the full-phrase level, not at the individual-character level.

Expected Outcome

• Users can more clearly understand which code to edit and how to edit it.
• Tutorial guidance becomes more direct without feeling overly hand-held.

Acceptance Criteria

• API Reference only shows APIs relevant to the current tutorial.
• Drag guidance (code-drag-hint) is removed.
• Diff comparison is shown at the full-phrase level.
• Copilot does not over-intervene when users can proceed independently.

[qingqing-ux]

Code PR

[qingqing-ux]

同步 6.26 会议结论
一、User Tutorial 产品设计原则

• Copilot 在 User Tutorial 中定位为幕后大脑，仅在学生无法完成时主动提醒，手把手教的感觉不能太重。

二、已确定（可执行）

• 内容展示
  • API Reference 仅展示当前课程涉及的 API。
• 引导策略
  • 移除拖拽引导（code-drag-hint）。
  • 保留代码输入引导（code-delete-hint、code-change-hint）。
  • Diff 比较以完整词组为单位，不针对单个字符。