GitHub Copilot's /chat/completions and /responses endpoints never surface
prompt-cache token counts for Claude models. Route Claude models (detected
by name pattern) to Copilot's Anthropic-native /v1/messages shim via a new
executeWithMessagesEndpoint(), translating OpenAI-shape requests to Claude
natively so cache_control gets injected and cached_tokens surface.
Also fixes translateRequest()'s internal _toolNameMap being sent upstream,
which made Anthropic's strict schema reject tool-call requests with a 400 —
now stripped and threaded through response state. Removes the now-dead
response_format Claude JSON-mode workaround.
542a088c04