feat: OpenMesh 基础平台与 MD/PDF 转换技能

- 后端: coworker 智能体框架, WS API, 文件上传, 附件处理
- 前端: Open WebUI, 文件全量走 upload API (含 MD/TXT/JSON 等文本类)
- 技能: md-to-office (pandoc + wkhtmltopdf)
- 修复: 上传文件路径丢失, Agent 搜索浪费, 输出文件跑到 uploads/
- 打包: PyInstaller one-dir, 预打包 pandoc/wkhtmltopdf/chromium

coworker/providers/__init__.py

@@ -0,0 +1,54 @@
+from .anthropic_provider import AnthropicProvider
+from .bedrock_provider import BedrockProvider
+from .base import (
+    AssistantTurn,
+    ModelCapabilities,
+    ProviderClient,
+    StreamChunk,
+    ToolCall,
+)
+from .capabilities import capabilities_for
+from .codex_provider import CodexProvider
+from .gemini_provider import GeminiProvider
+from .openai_provider import OpenAIProvider, resolve_api_key
+from .openai_responses import OpenAIResponsesProvider
+from .registry import (
+    ProviderDescriptor,
+    ProviderField,
+    build_provider_client,
+    descriptor_configured,
+    detect_provider,
+    get_descriptor,
+    provider_descriptors,
+    provider_names,
+    verify_provider_key,
+)
+from .router import ProviderRouter
+from .vertex_provider import VertexProvider
+
+__all__ = [
+    "AssistantTurn",
+    "ModelCapabilities",
+    "ProviderClient",
+    "StreamChunk",
+    "ToolCall",
+    "AnthropicProvider",
+    "BedrockProvider",
+    "CodexProvider",
+    "GeminiProvider",
+    "OpenAIProvider",
+    "OpenAIResponsesProvider",
+    "VertexProvider",
+    "resolve_api_key",
+    "capabilities_for",
+    "ProviderRouter",
+    "ProviderDescriptor",
+    "ProviderField",
+    "provider_descriptors",
+    "provider_names",
+    "get_descriptor",
+    "build_provider_client",
+    "descriptor_configured",
+    "detect_provider",
+    "verify_provider_key",
+]