fix: guard against empty tool_use/function.name in protocol conversion

[spock-wen]

Summary

Skip tool calls with empty function.name at all conversion points. Upstream providers occasionally return tool_calls with empty function.name, which produces downstream JSON with empty names that Claude Code rejects.

Changes

• Streaming response: check name.String() != "" (not just Exists)
• Non-streaming response: skip in convertOpenAINonStreamingToAnthropic
• Non-streaming alternative: skip in ConvertOpenAIResponseToClaudeNonStream (both content-array and message-level tool_calls paths)
• Request back-conversion: skip tool_use with empty name

Files

• internal/translator/openai/claude/openai_claude_request.go (+5, -1)
• internal/translator/openai/claude/openai_claude_response.go (+16, -4)

Test Plan

• go test ./test/... passes locally

[kittors]

Request changes. The non-streaming guards are useful, but the streaming fix is incomplete.

In convertOpenAIStreamingChunkToAnthropic, an empty function.name no longer emits content_block_start, but the accumulator still stores arguments. When finish_reason=tool_calls or [DONE] is processed, the existing finalization path still iterates every accumulator and can emit input_json_delta/content_block_stop for a tool block that was never started. That leaves orphan Anthropic stream events.

It also does not adjust stop_reason when all tool calls were skipped: tool_calls/function_call can still become tool_use even though no valid tool_use block was emitted. Request-side handling also needs to avoid empty/whitespace tool_use, empty tools/tool_choice names, and orphan tool_result messages for skipped tool_use ids.

A complete fix should track whether a tool content block has actually started, finalize only started blocks, map tool_calls to end_turn when no valid tool was emitted, trim whitespace-only names, and add regression tests for empty-name streaming, usage chunks, arguments-before-name, mixed valid/empty tools, non-streaming, and request conversion. See #430/#431 for the fuller implementation direction.