Keep the provider cost metric picker synchronized with the shared cost/token selection and guard invalid ledger clocks, update scheduling clocks, and null cost entries.

Verified head ae620a76d46c307ca3416506cd56162dab7c45af against main 2a02f6a. CI 34388445914 passed check, packaging, smoke, and the panel matrix; CodeQL and PR title passed. Codex completed without findings. Documentation and TODO remain consistent with the supported behavior; Unreleased records the picker fix.