refactor: remove screenshot functionality and headless_chrome dependency

Remove the screenshot capture system and associated UI components to simplify the codebase.

- Remove screenshot.rs command module and related functionality
- Remove headless_chrome dependency from Cargo.toml
- Update Cargo.lock to reflect dependency changes
- Remove screenshot handlers and UI from WebviewPreview component
- Clean up screenshot-related API calls and imports
- Remove camera icon and capture controls from preview interface

This reduces bundle size and eliminates an underutilized feature.

src-tauri/src/commands/agents.rs

@@ -5,7 +5,6 @@ use reqwest;
 use rusqlite::{params, Connection, Result as SqliteResult};
 use serde::{Deserialize, Serialize};
 use serde_json::Value as JsonValue;
-use std::path::PathBuf;
 use std::process::Stdio;
 use std::sync::Mutex;
 use tauri::{AppHandle, Emitter, Manager, State};