harden: end a site's unremembered connection when its address or wallet is removed (closes #245)

A site connected without "Remember" lives only in the background's
in-memory connectedSites map. Removing an address or deleting a wallet
dropped the remembered permissions but never told the background; the
entry went only as a side effect of the accountsChanged broadcast, which
empties the whole map when the active address changes.

dropSitePermissions(), shared by both removal paths, now sends
AUTISTMASK_ADDRESSES_REMOVED with the removed addresses, and the
background deletes their entries. Only the extension's own pages may
send it.

Model: opus-5-5

src/shared/walletDelete.js

@@ -12,12 +12,15 @@ function sameAddress(a, b) {
     return String(a).toLowerCase() === String(b).toLowerCase();
 }
 
-// Forget every site permission held against the given addresses.
+// Forget every site permission held against the given addresses: the
+// remembered ones in `state`, and the connections approved without
+// "Remember", which only the background holds, in memory.
 function dropSitePermissions(state, addresses) {
     for (const addr of addresses) {
         delete state.allowedSites[addr];
         delete state.deniedSites[addr];
     }
+    notify({ type: "AUTISTMASK_ADDRESSES_REMOVED", addresses });
 }
 
 // Remove wallet `walletIdx` from `state` and repair the derived state.