test: cover protocol current input defaults

[Activer007]

Summary

• add OpenAI Chat and Responses coverage for production-style current-input defaults: hybrid_recent context, neutral randomized filenames, and neutral live prompts
• harden Claude and Gemini current-input tests with the same default strategy and filename assertions
• verify prompt-visible current-input context does not expose DS2API implementation terms

Tests

• go test ./internal/httpapi/openai
• go test ./internal/httpapi/claude
• go test ./internal/httpapi/gemini
• ./scripts/lint.sh
• ./tests/scripts/check-refactor-line-gate.sh
• ./tests/scripts/run-unit-all.sh
• npm run build --prefix webui