feat(web-search): remove built-in web_search tool, replace with MCP-based approach (#3502)

* feat(web-search): add GLM (ZhipuAI) web search provider

- Add GlmProvider class implementing BaseWebSearchProvider using the
  ZhipuAI Web Search API (https://open.bigmodel.cn/api/paas/v4/web_search)
- Support multiple search engines: search_std, search_pro, search_pro_sogou,
  search_pro_quark
- Support optional config: maxResults, searchIntent, searchRecencyFilter,
  contentSize, searchDomainFilter
- Truncate query to 70 characters per API limit
- Register 'glm' in the provider discriminated union (types.ts) and
  createProvider() switch (index.ts)
- Add GlmProviderConfig to settingsSchema, ConfigParams, and Config class
- Add --glm-api-key CLI flag and GLM_API_KEY env var support in webSearch.ts
- Forward GLM_API_KEY in sandbox environment
- Update provider priority list: Tavily > Google > GLM > DashScope
- Add 17 unit tests for GlmProvider and 4 integration tests in index.test.ts
- Update docs/developers/tools/web-search.md with GLM configuration,
  env vars, CLI args, pricing, and corrected DashScope billing info
- Fix stale OAuth/free-tier references in web-search.md

Closes #3496

* docs(web-search): fix DashScope note and add GLM server-side limitations

* fix(web-search): make DashScope provider work with standard API key, remove qwen-oauth dependency

- DashScopeProvider.isAvailable() now checks config.apiKey instead of authType
- Remove OAuth credential file reading and resource_url requirement
- Use standard DashScope endpoint: dashscope.aliyuncs.com/api/v1/indices/plugin/web_search
- Read DASHSCOPE_API_KEY env var and --dashscope-api-key CLI flag
- Forward DASHSCOPE_API_KEY into sandbox environment
- Update integration test to detect DASHSCOPE_API_KEY
- Update docs to reflect new API key based configuration

* feat(web-search): remove built-in web search tool

The web_search tool and all related provider implementations are removed.
Web search functionality will be provided via MCP integrations instead,
which is the direction the broader agent ecosystem is moving.

Removed:
- packages/core/src/tools/web-search/ (entire directory)
- packages/cli/src/config/webSearch.ts
- integration-tests/cli/web_search.test.ts
- ToolNames.WEB_SEARCH, ToolErrorCode.WEB_SEARCH_FAILED
- webSearch config in ConfigParams, Config class, settingsSchema
- CLI options: --tavily-api-key, --google-api-key, --google-search-engine-id,
  --glm-api-key, --dashscope-api-key, --web-search-default
- Sandbox env forwarding for TAVILY/GLM/DASHSCOPE/GOOGLE search keys
- web_search from rule-parser, permission-manager, speculation gate,
  microcompact tool set, and builtin-agents tool list

* fix: remove websearch reference

* docs: remove websearch tool

* docs: add break change guide

* fix review

docs/developers/tools/introduction.md

@@ -46,7 +46,6 @@ Qwen Code's built-in tools can be broadly categorized as follows:
 - **[File System Tools](./file-system.md):** For interacting with files and directories (reading, writing, listing, searching, etc.).
 - **[Shell Tool](./shell.md) (`run_shell_command`):** For executing shell commands.
 - **[Web Fetch Tool](./web-fetch.md) (`web_fetch`):** For retrieving content from URLs.
-- **[Web Search Tool](./web-search.md) (`web_search`):** For searching the web.
 - **[Multi-File Read Tool](./multi-file.md) (`read_many_files`):** A specialized tool for reading content from multiple files or directories, often used by the `@` command.
 - **[Memory Tool](./memory.md) (`save_memory`):** For saving and recalling information across sessions.
 - **[Todo Write Tool](./todo-write.md) (`todo_write`):** For creating and managing structured task lists during coding sessions.
@@ -58,5 +57,6 @@ Additionally, these tools incorporate:
 - **[MCP servers](./mcp-server.md)**: MCP servers act as a bridge between the model and your local environment or other services like APIs.
   - **[MCP Quick Start Guide](../mcp-quick-start.md)**: Get started with MCP in 5 minutes with practical examples
   - **[MCP Example Configurations](../mcp-example-configs.md)**: Ready-to-use configurations for common scenarios
+  - **[Web Search via MCP](./web-search.md)**: Connect to web search services (Bailian, Tavily, GLM) through MCP
   - **[MCP Testing & Validation](../mcp-testing-validation.md)**: Test and validate your MCP server setups
 - **[Sandboxing](../sandbox.md)**: Sandboxing isolates the model and its changes from your environment to reduce potential risk.