feat: add FetchUrlTool with proxy support and cross-OS path sanitization

- Implement native FetchUrlTool using reqwest for HTTP fetching, which respects HTTP_PROXY, HTTPS_PROXY, and NO_PROXY natively.
- Introduce sanitize_path in utils to bidirectionally handle Windows/WSL path mapping, applying it to various search/git handlers.
- Update .gitignore to exclude mcp_store.redb and tantivy_index.

server/src/tools.rs

@@ -1033,3 +1033,12 @@ pub struct ClipboardTool {
     /// Image path (for 'write').
     pub image_path: Option<String>,
 }
+
+/// Fetch content from a URL via an HTTP GET request natively (supports proxy config via environment variables: HTTP_PROXY, HTTPS_PROXY, NO_PROXY).
+#[derive(Debug, Deserialize, Serialize, JsonSchema)]
+pub struct FetchUrlTool {
+    /// URL to fetch content from.
+    pub url: String,
+    /// Optional custom user-agent string.
+    pub user_agent: Option<String>,
+}