Prompt-cache diff tracking now covers thinking-mode and thinking-display changes

Claude Code keeps an internal record of what changed between requests (things like the model, the system prompt, and the reasoning effort) to decide whether it can reuse the cached prompt or needs to send a fresh one, and to help with diagnostics. This record now also tracks two more fields:

• thinkingModeChanged, whether extended thinking mode was turned on or off
• thinkingDisplayChanged, whether the display of that thinking changed

Both fields record the previous and new values, matching how the existing fields already work.