feat: add --cookie-file support for JSON cookie files

- --cookie-file reads Chrome extension format ([{name, value, domain, ...}])
- Works with EditThisCookie, Cookie-Editor, and similar browser extensions
- Merges with --cookie when both provided
- MCP scrape tool now accepts cookies parameter
- Closes #7

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/webclaw-mcp/src/tools.rs

@@ -18,6 +18,8 @@ pub struct ScrapeParams {
     pub only_main_content: Option<bool>,
     /// Browser profile: "chrome" (default), "firefox", or "random"
     pub browser: Option<String>,
+    /// Cookies to send with the request (e.g. ["name=value", "session=abc123"])
+    pub cookies: Option<Vec<String>>,
 }
 
 #[derive(Debug, Deserialize, JsonSchema)]