Adds the Copilot provider: device-flow login modal support, copilot_internal/v2/token exchange with a direct-Bearer fallback, and routing across the three codecs, per the dual-path mitigation noted for Copilot token variance.
Adds a bundled models.dev snapshot plus harness-providers::modelsdev to resolve model metadata, and wires live cost display into the TUI's input bar and message state, updating the render snapshots accordingly.
Extends the model catalog with per-token pricing and accumulates cost per engine step, threading the running total through the store and up into harness-app so it can be surfaced in the UI.
Adds harness-providers::auth, a persisted auth.json credential store for provider tokens, laying the groundwork for Copilot's device-flow login and token refresh.
Adds both OpenAI codecs — chat completions and the newer responses API — plus the OpenAiProvider and registry wiring, so the same session can run against OpenAI in addition to Anthropic.
darman