fix(llm): restore OpenAI reasoning streams - #28552

Summary

• parse OpenAI-compatible chat reasoning_content deltas into common reasoning events
• parse OpenAI Responses reasoning summary/text stream events
• add deterministic parser regressions and a recorded OpenAI Responses reasoning cassette

Tests

• bunx prettier --write packages/llm/src/protocols/openai-chat.ts packages/llm/src/protocols/openai-responses.ts packages/llm/src/protocols/utils/lifecycle.ts packages/llm/test/provider/golden.recorded.test.ts packages/llm/test/provider/openai-chat.test.ts packages/llm/test/provider/openai-responses.test.ts packages/llm/test/recorded-golden.ts packages/llm/test/recorded-scenarios.ts packages/llm/test/fixtures/recordings/openai-responses/openai-responses-gpt-5-5-reasoning.json
• bunx oxlint packages/llm/src/protocols/openai-chat.ts packages/llm/src/protocols/openai-responses.ts packages/llm/src/protocols/utils/lifecycle.ts packages/llm/test/provider/golden.recorded.test.ts packages/llm/test/provider/openai-chat.test.ts packages/llm/test/provider/openai-responses.test.ts packages/llm/test/recorded-golden.ts packages/llm/test/recorded-scenarios.ts
• bun test --timeout 30000 test/provider/openai-chat.test.ts test/provider/openai-responses.test.ts test/provider/openai-compatible-chat.test.ts test/provider/openrouter.test.ts test/provider/golden.recorded.test.ts
• bun test --timeout 30000 test/provider/golden.recorded.test.ts -t "uses reasoning"
• bun typecheck
• bun test --timeout 30000 test/session/llm-native.test.ts test/session/llm.test.ts -t "reasoning|native"
• push hook: bun turbo typecheck