fix(openai): handle compatible stream tool calls

[kevinn142857]

Summary

• accept OpenAI-compatible stream tool call variants with top-level name/function_name/tool_name and arguments/input fields
• reject streamed tool calls that still lack a function name with a clear provider error instead of surfacing Tool does not exist.
• add stream parser tests for standard OpenAI chunks, compatible variants, and missing names

Tests

• npm run build
• node --test --test-force-exit --test-timeout 60000 "dist/tests/**/*.test.js"