fix(adapters): filter empty text parts in message conversion

[dingyi222666]

问题

多模态消息转换时，空文本 part（如 {type:'text', text:''}）会被原样透传到模型请求中，例如 Gemini 请求里出现 {"text":""} 空 text part，可能导致部分 API 报错。

空 text part 的来源包括：fileInsertPrompt 未配置（默认空字符串）时 read_files 注入的多模态消息、content 为空字符串的消息等。

修复

在适配器消息转换层统一过滤空文本 part（最小判断 length > 0）：

• shared-adapter (langchainMessageToOpenAIMessage): 数组 content 中空 text part 丢弃 —— 覆盖所有 OpenAI 兼容适配器（openai / openai-like / azure-openai / deepseek / qwen / doubao / rwkv / hunyuan / spark / wenxin / zhipu）
• adapter-gemini (processGeminiContentParts + langchainMessageToGeminiMessage): 空 text part 丢弃；字符串 content 为空时不生成 [{text:''}]
• adapter-claude (processMessageContent): 空 text block 丢弃

ollama / dify 走字符串/文本提取路径，无空 part 结构问题，无需修改。

Validation

• yarn fast-build (shared-adapter / adapter-gemini / adapter-claude) 0 errors

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Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 2684fc2b-2a2b-4c60-9609-28a8d720998e

📥 Commits

Reviewing files that changed from the base of the PR and between ca1177d and eb7dd2a.

📒 Files selected for processing (3)

• packages/adapter-claude/src/utils.ts
• packages/adapter-gemini/src/utils.ts
• packages/shared-adapter/src/utils.ts

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Walkthrough

Changes

空文本过滤

Layer / File(s)	Summary
共享消息内容过滤 packages/shared-adapter/src/utils.ts	新增文本内容识别，并在消息映射时过滤空文本。其他内容类型保持原有处理。
供应商适配器过滤 packages/adapter-claude/src/utils.ts, packages/adapter-gemini/src/utils.ts	Claude 和 Gemini 适配器不再生成空文本块或空文本 part。非空文本保持原有转换。

Estimated code review effort: 1 (Trivial) | ~5 minutes

Suggested reviewers: cooksleep

Poem

我是一只检查空文本的兔，
轻轻跳过空白块。
非空文字仍保留，
Claude、Gemini 都整齐，
共享映射也清爽。

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/multimodal

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