feat: avoid opening duplicate tabs in CDP browser on update

[atomantic]

Summary

When running update.sh or update.ps1, PortOS invokes scripts/open-ui-in-browser.js to auto-open the dashboard in the PortOS-managed CDP browser. Previously, it always navigated a fresh tab, creating duplicate tabs whenever updates were executed repeatedly with PortOS already open.

This change:

• Queries open CDP pages and checks for an existing PortOS tab before opening a new tab.
• Matches existing tabs against the target URL, loopback origins (ports 5555, 5553, 5554), Tailscale hostnames (*.ts.net), or PortOS page titles on PortOS ports.
• Skips launching if a tab is already open, logging that PortOS is already open.
• Only launches a new pinned tab if no PortOS tab exists in CDP.
• Retries connection during cold starts so tabs in an existing or restoring browser session are recognized once CDP is reachable.

Test plan

• Added unit tests in scripts/open-ui-in-browser.test.js verifying isPortOsPage, findExistingPortOsTab, and openPortOsUi.
• Verified skipping launch when a tab is already open and launching when no PortOS tab is present.
• Verified retrying during cold launch and detecting restored tabs.
• Verified server and client unit tests pass.