CLI Proxy API 6.8.21 አውርድ

Changelog
- 709d999 Add usage to /v1/completions
- b2b1752 Merge branch 'pr-1624' into dev
- 76294f0 Merge pull request #1608 from thebtf/fix/tool-reference-proxy-prefix-mainline
- 55f9381 Merge pull request #1618 from alexey-yanchenko/fix/completions-usage
- 252f7e0 Merge pull request #1625 from thebtf/feat/tool-prefix-config
- 2d12bec Merge pull request #1627 from thebtf/fix/reasoning-effort-clamping
- fff8664 Merge pull request #1628 from thebtf/fix/masquerading-headers
- 9c04044 Merge pull request #1635 from thebtf/fix/openai-translator-tool-streaming
- 9261b0c feat: add per-auth tool_prefix_disabled option
- 98f0a3e fix: add proxy_ prefix handling for tool_reference content blocks (#1)
- 2ea9526 fix: clamp reasoning_effort to valid OpenAI-format values
- 5fa23c7 fix: handle tool call argument streaming in Codex→OpenAI translator
- 603f06a fix: handle tool_reference nested inside tool_result.content[]
- 24c1861 fix: skip built-in tools in tool_reference prefix + refactor to switch
- 7cc7254 fix: skip proxy_ prefix for built-in tools in message history
- 73dc0b1 fix: update Claude masquerading headers and make them configurable