Fix s02 orphaned tool_result repair ordering in normalize_messages

[shyboy429]

Summary

This fixes normalize_messages() so missing tool_result blocks are inserted
immediately after the assistant message that contains the originating tool_use,
instead of being appended to the end of the message list.

Why

Anthropic's Messages API requires each tool_result block to correspond to a
tool_use block in the previous assistant message. Appending orphaned
tool_result blocks to the end can break that invariant and cause 400 errors.

Changes

• repair orphaned tool_result blocks in-place after the matching assistant message
• update the Chinese teaching doc example to match the implementation

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