Browser pairing, notifications, element hiding; drop the top bar

Pairing decrypts a Chromium browser's cookie store (PBKDF2-HMAC-SHA1
against its Keychain key, then AES-128-CBC) and injects the result into
WKHTTPCookieStore. Only the configured apps' hosts and their sign-in
hosts survive the filter. Browsers are offered most-recently-used first,
since the first entry becomes the default and someone with four
Chromium browsers installed wants the one they actually browse in.

WKWebView defines window.Notification but it does nothing: constructing
one throws no error and shows no banner, so a page believes it notified
you. Measured on the machine as `api=function shim=no` before the shim
was made unconditional; `from page: Odoo - Test notification -> raised`
after.

Anything on a page can be right-clicked away. The rule is re-asserted on
every navigation, because the injected script only carries a snapshot
from when the view was built and a selector added since would otherwise
come back on reload.

The top bar is gone. Navigation lives beside the cog, the nav carries
the traffic lights, and two-finger swipe goes back and forward.

The seed is now the real app list, scoped to exact hosts so a Drive link
inside Gmail switches rather than being swallowed.

src-tauri/src/routing.rs

@@ -65,6 +65,12 @@ pub fn host_matches(host: &str, scope: &str) -> bool {
     host == scope || host.ends_with(&format!(".{scope}"))
 }
 
+/// The sign-in hosts, for the cookie import — a session for a tool is no use
+/// without the identity provider's cookie that vouches for it.
+pub fn identity_providers() -> &'static [&'static str] {
+    IDENTITY_PROVIDERS
+}
+
 fn is_identity_provider(host: &str) -> bool {
     IDENTITY_PROVIDERS.iter().any(|p| host_matches(host, p))
 }