Lucas/native messaging host

[lukitasxue]

Summary

Adds the Chrome Native Messaging host needed for the Taskmaster Browser Monitor extension to communicate with the local Taskmaster app.

This moves the extension toward Chrome’s official local-app communication path instead of relying only on the earlier prototype bridge.

What changed

• Adds the native messaging host manifest for com.taskmaster.browser_monitor.
• Adds Windows install/uninstall scripts for registering the host under the current user.
• Adds the local native host script that receives extension messages.
• Documents setup, install, uninstall, and troubleshooting steps.
• Keeps the data flow local to the user’s machine.

Behavior notes

• The extension sends active tab metadata to the local Taskmaster app through the native host.
• The host is intended to be installed locally by the user/developer.
• No page contents, cookies, form fields, or browsing history API are collected.
• This PR focuses on the connection layer only, not classification or review UI.

Test plan

• Run syntax check for the host script.
• Install the native host with the Windows install script.
• Restart Chrome/Opera GX if needed.
• Start Taskmaster.
• Start a focus session.
• Open browser tabs and confirm tab metadata reaches Taskmaster.
• Stop the focus session and confirm browser monitoring stops.