docs(pages): update website to reflect OpenAI Responses API protocol support

[lizhengfeng101]

Background

PR #363 added a third LLM protocol openai-responses (OpenAI Responses API /v1/responses) alongside the existing anthropic and openai (Chat Completions) protocols. The project website (pages/) still references only the original two protocols in several places.

What needs to change

Update the following i18n strings across all language files (en.ts, zh.ts, ja.ts):

1. features.feat3Desc

The feature description currently says the project supports "both Anthropic Messages API and OpenAI Chat Completions API". It should now mention all three protocols:

• Anthropic Messages API
• OpenAI Chat Completions API
• OpenAI Responses API (new)

2. docs.configManualCustomNote

Currently says:

Supported protocols: anthropic, openai.

Should be updated to:

Supported protocols: anthropic, openai, openai-responses.

Files to modify

• pages/src/i18n/en.ts
• pages/src/i18n/zh.ts
• pages/src/i18n/ja.ts

Acceptance criteria

• All three language files are updated consistently
• The wording is natural in each language (not machine-translated)
• No other content or formatting changes are introduced
• npm run build in the pages/ directory succeeds without errors

Reference

• PR feat: Add OpenAI Responses API support and refactor protocol handling #363: feat: Add OpenAI Responses API support and refactor protocol handling
• The three protocols are: anthropic, openai, openai-responses