Add toggle to hide extended thinking blocks in VS Code extension

The VS Code extension currently displays extended thinking/reasoning blocks inline during responses. There is no way to suppress or collapse these automatically. For users who do not need to see the model's reasoning process, this creates significant visual noise and makes responses harder to read.

Request: Add a setting in the VS Code extension (e.g. claude.showThinking: true/false) to suppress or auto-collapse thinking blocks. A spinner or simple "thinking..." indicator would be sufficient.