docs(config): document parser_api settings

[r266-tech]

Summary

• Document the new parser_api/Understanding API config added on feat/knowledge_parser by feat: match response api #2559.
• Cover routing conditions, required host/api_key fields, upload and timeout knobs, and host /api/v3 normalization.
• Add parser_api to the EN/ZH full schema examples.

Verification

• Source-checked ParserApiConfig and ParserRouter on feat/knowledge_parser.
• python3 parsed the EN/ZH Full Schema JSON blocks.
• git diff --check

[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🎫 Ticket compliance analysis ✅ 2559 - Fully compliant Compliant requirements: Added documentation for the new parser_api/Understanding API config Covered routing conditions, required host/api_key fields, upload and timeout knobs, and host /api/v3 normalization Added parser_api to the EN/ZH full schema examples

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🏅 Score: 100

🧪 No relevant tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ No major issues detected

[github-actions]

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