test: Native Anthropic pass-through — feature coverage tests

[HXYerror]

Part of #38. Depends on #39, #40, #41.

Goal

Test coverage for the native Anthropic pass-through path added in #39–#41.

Tasks

• tests/messages-native-dispatch.test.ts — unit tests for the dispatch logic in feat: Route dispatch — detect native-capable models, branch to pass-through #40:

  • claude-sonnet-4.5 → native path
  • claude-sonnet-4 → translation path
  • gpt-4o → translation path (no change)
  • Alias "sonnet-4.5" → resolves → native path

• tests/messages-native-passthrough.test.ts — integration tests (mock upstream):

  • Basic chat: response shape is Anthropic {type:"message", content:[...]} (NOT OpenAI {choices:[...]})
  • Thinking block: response includes {type:"thinking", thinking:"...", signature:"..."}
  • Tool use: response includes {type:"tool_use", name:"...", input:{...}}
  • Streaming: SSE events are message_start / content_block_* / message_delta / message_stop
  • Multi-turn with thinking: echoed signature in input is forwarded byte-exact to upstream mock

• tests/anthropic-types.test.ts — verify AnthropicThinkingBlock has signature? field, and usage shape includes cache_creation

• Regression: existing tests/anthropic-request.test.ts and tests/anthropic-response.test.ts still pass (translation path unchanged)

Acceptance criteria

• bun test passes with native path tests
• Mock upstream confirms no translation happens for native-path models (request body sent to mock is unchanged Anthropic JSON)
• Mock upstream confirms translation happens for legacy-path models (request body is OpenAI JSON)

[HXYerror]

Tests added in PR #48 — 19 tests covering buildUpstreamPayload (T1-T6), isNativeAnthropicModel (T5-T9), and isAdaptiveThinkingModel boundaries (B1-B6). 61 tests passing.