feat(docs): add --lang to docs +fetch v2 for cite user display language

[herbertliu]

What

Adds a --lang flag to docs +fetch v2 (OpenAPI path) so <cite type="user"> display names are returned in the requested language.

• v2FetchFlags(): new --lang flag (e.g. zh_cn / en_us / ja_jp)
• buildFetchBody(): injects body["lang"] with priority explicit --lang > runtime.Lang() (user default) > omit
• RuntimeContext.Lang(): now nil-Config safe
• lark-doc skill fetch reference: documents --lang
• Tests: explicit lang + omitted-when-unset

Maps to OpenAPI request field OpenDocsAIFetchDocumentRequest.Lang (api.json="lang", field-id 8, already on master). Backend passthrough (ai_edit + office_ai_sdk) tracked separately.

Verify

docs +fetch --api-version v2 --doc <token> --lang ja_jp --dry-run   # body carries "lang":"ja_jp"
docs +fetch --api-version v2 --doc <token> --dry-run                 # falls back to runtime user lang, or omits

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added a hidden CLI --lang option to control citation display language for document fetches (e.g., zh_cn, en_us, ja_jp); when omitted, the user's configured language is used.

• Bug Fixes

  • Improved handling when a user's language preference is unset so language resolution falls back sensibly.

• Documentation

  • Docs updated with --lang usage, guidance for writing messages to documents, and updated rules/examples for the sub-page-list resource.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

This PR adds a hidden --lang flag to the v2 OpenAPI document fetch to control user-citation display language, injects that value (or runtime fallback) into the fetch request body, adds defensive nil-handling in RuntimeContext.Lang(), includes tests for the behaviour, and updates documentation.

Changes

Language Flag Support for Document Fetch v2

Layer / File(s)	Summary
RuntimeContext.Lang() nil-safety shortcuts/common/runner.go	Added nil-check for ctx.Config to return empty string instead of panicking.
V2 fetch lang flag and injection shortcuts/doc/docs_fetch_v2.go	Added hidden --lang flag and injectLang used by buildFetchBody: prefer explicit flag, else runtime.Lang(), else omit lang.
V2 fetch lang tests and runtime setup shortcuts/doc/docs_fetch_v2_test.go	Added parallel tests verifying explicit lang is included and omitted when empty; registered lang flag on test cobra.Command.
Document fetch CLI docs skills/lark-doc/references/lark-doc-fetch.md	Documented --lang usage for <cite type="user"> language, omission/fallback rules, and server-side format tolerance.
Doc XML updates and username-write rules skills/lark-doc/references/lark-doc-xml.md	Added <sub-page-list> resource block, marked it copy-supported, inserted example, and added username-writing rules requiring <cite type="user" user-id="..."> with lookup guidance.
IM -> Document username citation guidance skills/lark-im/SKILL.md	Added "Writing Messages to Lark Documents" section requiring <cite> for open_id-based users and describing resolution workflow when only names exist.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• larksuite/cli#1132: Related previous changes to RuntimeContext.Lang() implementation and language-resolution path.
• larksuite/cli#1168: Overlapping documentation edits for <sub-page-list> in the lark-doc XML reference.

Suggested labels

feature, documentation, size/M

Suggested reviewers

• SunPeiYang996
• fangshuyu-768

Poem

🐰 I hop across flags, a tiny guide,
--lang tucked close to names worldwide,
Nil-checked paths keep panics at bay,
Tests nod yes, docs show the way,
User cites now speak the tongue they tried.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 37.50% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: adding a --lang flag to docs +fetch v2 for controlling cite user display language.
Description check	✅ Passed	The description covers all required template sections: Summary explains motivation, Changes lists main modifications, Test Plan includes verification examples, and Related Issues is noted.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/docs-cite-user-lang-bq

Warning

Review ran into problems

🔥 Problems

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