add deepseek direct via userToken

track tokens openrouter with apikey

fix imports chat.go

add deepseek via openrouter

fix undefined TrackUsage and cleanup keys.go

enable token tracking on handlers

fix auth flow for RWPX keys

fix: improve streaming tool_call block detection and add debug logging

fix: improve tool calling reliability with multi-format parsing and Delta pointer fix

feat: support tool/function calling (OpenAI compatible)

refactor: split internal package into domain-based sub-packages