harden: list and end site connections made without Remember in Settings (closes #406)

A site allowed without "Remember" lives only in the background's
in-memory connectedSites map. Settings never listed it, and
AUTISTMASK_REMOVE_SITE, sent on every remove, did nothing, so the user
could not end such a connection.

Settings now asks the background for those sites and lists them under
Connected Sites. Removing a site from Allowed Sites or Connected Sites
drops its remembered entry under every address and sends
AUTISTMASK_REMOVE_SITE with the hostname; the background deletes every
matching connectedSites entry and sends accountsChanged with an empty
list to the site's tabs. Only the extension's own pages may send either
message.

Model: opus-5-5

README.md

@@ -1582,8 +1582,14 @@ view would leave a wallet one click from deletion.
           a value carrying its unit, hex (`0x10`) or exponent (`1e3`) notation —
           is refused with a flash message and the field snaps back to the stored
           threshold, so a number the user did not type is never stored.
-    - Allowed Sites: list with remove buttons
-    - Denied Sites: list with remove buttons
+    - Allowed Sites: the hostnames remembered as allowed, under any address,
+      with remove buttons
+    - Connected Sites: the hostnames of the sites allowed without "Remember my
+      choice" that are still connected, with remove buttons. Only the background
+      holds these, in memory, and Settings asks it for them with
+      `AUTISTMASK_GET_CONNECTED_SITES`
+    - Denied Sites: the hostnames remembered as denied, under any address, with
+      remove buttons
     - About: project link, license, author, version, release date, and the
       commit, which links to the commit in the repository
     - Debug: hidden until revealed, then an "Enable debug mode" checkbox that
@@ -1594,8 +1600,15 @@ view would leave a wallet one click from deletion.
     - `[recovery phrase]` on an HD wallet → **ShowRecoveryPhrase**
     - `[x]` on a wallet → **DeleteWallet**
     - Tap wallet name → inline rename field (no screen change)
-    - `[x]` on a tracked token or a site → removes it in place (no screen
-      change)
+    - `[x]` on a tracked token → removes it in place (no screen change)
+    - `[x]` on an allowed or connected site → disconnects that site, in place:
+      its hostname is dropped from Allowed Sites under every address, and
+      `AUTISTMASK_REMOVE_SITE` has the background end every connection approved
+      without "Remember" from an origin with that hostname, under any address,
+      and send `accountsChanged` with an empty list to the site's open tabs.
+      Only the extension's own pages may send either message
+    - `[x]` on a denied site → forgets the refusal, in place; it connects
+      nothing and tells the background nothing
     - Ten clicks on the version → reveals the Debug well (no screen change)
     - "Back" (or Settings gear again) → previous screen (Home)
 
@@ -1790,7 +1803,8 @@ view would leave a wallet one click from deletion.
 - **Transitions**:
     - "Allow" / "Deny" → closes popup (returns result to background script; the
       choice is persisted to the allowed or denied list when "Remember" is
-      checked)
+      checked, and an "Allow" without it is listed under Connected Sites in
+      **Settings**)
     - Popup closed without answering → treated as a denial
 
 #### TxApproval (`approve-tx`)