feat(extension): support multiple concurrent client connections

[Matthew Goodwin (m4ttheweric)]

Summary

• The bridge extension previously allowed one active client; a new connection force-disconnected the previous one ("Another connection is requested"). It now keeps a connection map so multiple MCP clients (e.g. parallel agent sessions) can drive the browser concurrently.
• Each connection gets its own labeled Chrome tab group (<client name> #<n>, rotating colors). Per-connection tab isolation follows from the existing per-connection _attachedTabs filtering.
• The extension's own UI pages are excluded from popup forwarding and group auto-attach: Chrome records the previously active tab as a new connect page's opener, which would otherwise hand one client's connect page to another client.
• Token-bypass connections no longer steal window focus; explicit "Allow & select" still focuses the picked tab. Status page lists all connected clients with per-client disconnect.

[Matthew Goodwin (m4ttheweric)]

@microsoft-github-policy-service agree

[Devin Rousso (dcrousso)]

please take a look at the contribution guide before creating a PR

To maintain project quality and focus, Playwright requires a corresponding issue for every contribution, with the exception of minor documentation fixes.