v0.2.0: LM Studio engine

Adds a second local engine: any chat model served by LM Studio.

• How it answers: each option is shown as a letter and the model replies with one token. The confidence is the probability the model gave each letter (logprobs), not a score it writes about itself.
• No thinking: reasoning is turned off (reasoning_effort: none)
• Where to choose it: engine selector in the web UI; --engine lmstudio, --model and --lmstudio-url in the CLI
• Optional API key: read from LMSTUDIO_API_KEY
• New example: severity (score) example

Results on the bundled examples (Qwen 3.5 4B, laptop CPU):

	Laya	LM Studio
choice / noul	86–100%	100%
score (severity)	10/14	11/14
Time per row (3 questions)	~0.6 s	~14 s

score remains experimental on both engines.