feat(tools): add native Pushover tool with priority and sound support

- Implements Pushover API as native tool (reqwest-based)
- Supports message, title, priority (-2 to 2), sound parameters
- Reads credentials from .env file in workspace
- 11 comprehensive tests covering schema, credentials, edge cases
- Follows CONTRIBUTING.md tool implementation patterns

src/tools/mod.rs

@@ -19,6 +19,7 @@ pub mod image_info;
 pub mod memory_forget;
 pub mod memory_recall;
 pub mod memory_store;
+pub mod pushover;
 pub mod schedule;
 pub mod screenshot;
 pub mod shell;
@@ -45,6 +46,7 @@ pub use image_info::ImageInfoTool;
 pub use memory_forget::MemoryForgetTool;
 pub use memory_recall::MemoryRecallTool;
 pub use memory_store::MemoryStoreTool;
+pub use pushover::PushoverTool;
 pub use schedule::ScheduleTool;
 pub use screenshot::ScreenshotTool;
 pub use shell::ShellTool;
@@ -141,6 +143,7 @@ pub fn all_tools_with_runtime(
             security.clone(),
             workspace_dir.to_path_buf(),
         )),
+        Box::new(PushoverTool::new(workspace_dir.to_path_buf())),
     ];
 
     if browser_config.enabled {