Add an in-editor browser surface

[felipeorlando]

Problem

MonoCode can open external URLs with the system browser and preview repository files, but it has no browser surface inside the workspace. Testing a local web app or following project links breaks the editor/session flow.

The closed upstream PR hardbeat920#48 added remote browser access to MonoCode; it did not add a browser inside MonoCode.

Proposed first slice

• Add a browser tab/pane type alongside files, diffs, terminals, and sessions.
• Support an address field plus Back, Forward, Reload, and Open externally.
• Support http://localhost/loopback development URLs and normal HTTPS pages.
• Keep each browser tab scoped to the current project/session layout and restore its URL with the workspace.
• Isolate page content from privileged Tauri commands; arbitrary sites must not inherit desktop capabilities.

Agent/browser automation can be a later issue. The first slice is a reliable human-operated embedded browser.

Existing work checked

• No browser tab/surface exists in current source.
• External links use @tauri-apps/plugin-opener.
• Upstream PR Add browser remote access hardbeat920/monocode#48 (closed) concerns remotely controlling the MonoCode UI from a browser and is not a duplicate.

Acceptance criteria

• A user can open a URL as a workspace tab or split pane.
• Basic navigation works for HTTPS and local development servers.
• Browser state participates in the existing tab/pane lifecycle.
• Untrusted pages cannot invoke privileged MonoCode/Tauri APIs.
• The user can always hand the page off to the system browser.