[BUG] Claude in Chrome: tabs created while Chrome is only hosting an installed web app (PWA) are invisible; only the debugging banner appears in the PWA window. Plus [FEATURE] per-PWA enable/disable

What happened
Computer A has no regular Chrome windows open — only an installed Chrome web app (Evernote). Chrome runs in the background to host the app, so the Claude extension in that profile stays connected to the account. A Claude session started from Computer B was routed to that connection. The extension created a tab group, opened tabs, loaded pages, ran JavaScript, and attempted downloads. None of those tabs appeared in any visible window. The only sign of activity was the "Claude started debugging this browser" banner at the top of the Evernote window. Downloads never showed up anywhere the user could see, and the user spent a long time troubleshooting what looked like broken downloads on the wrong machine.

Expected
If the extension acts in a Chrome that only hosts a PWA, the tabs it creates should be visible (open a normal browser window, or otherwise surface them). It should not create tabs that can't be seen or supervised. Downloads started from those tabs should behave normally and be visible.

Why it matters

• Tabs being driven with no visible window can't be supervised.
• The user reasonably believes Chrome isn't running on that machine.
• list_connected_browsers gave no way to tell this was a PWA-only host, or which machine it was on. isLocal was false for both browsers (see #78096).

Requested

1. Fix the invisible tabs: tabs created by the extension should always be in a visible, normal browser window.
2. Per-PWA setting, both directions: a per-app switch in the extension (e.g. "Allow Claude in this app"), so it can be on for some web apps and off for others, with a sensible default.
3. Identify PWA-only hosts: mark browsers whose only open windows are PWAs in list_connected_browsers, and ask for confirmation before acting in one.
4. Better device identification: hostname, OS user, profile name, and whether the browser is on the machine running the Claude session (see #77605).

Environment

• Claude in Chrome 1.0.94 on macOS; Chrome 154
• Claude desktop app (Cowork) session
• Two Macs signed into the same account; the PWA-only host was running the Evernote installed web app

Related: #77605, #77239, #78096