Expose Jev's confidence and probabilities (route_details)

[TheCoder30ec4]

Motivation

Jev returns a confidence value and a probability for each candidate, but route() throws them away. Callers could use them to fall back to a safe default when confidence is low, to log decisions, or to A/B test.

Proposal

Keep route() returning a plain str (no breaking change) and add:

result = router.route_details(task)
result.model          # "openai/gpt-6-luna"
result.confidence     # 0.95 or None (e.g. when Jev was skipped)
result.probabilities  # {"openai/gpt-6-luna": 0.96, ...}, keyed by real model id, not alias
result.candidates     # ids that passed the limits
result.rejected       # {model_id: reason}

Both backends need mapping: OpenRouter answers use aliases m0..mN, and Jev returns data.probabilities.

Done when

• Works for both backends and for the case where only one model is left
• Tests plus a README example

[Ansh0305]

Assign me this one,