harden: lost-password confirmation refuses empty input and ignores invisible characters (closes #336)

A wallet named only with spaces compared equal to an empty field, so
typing nothing would have deleted it, and a zero-width space in a name
made the name impossible to type back.

An empty typed confirmation is now refused whatever the name is. The
characters src/shared/symbolSpoof.js already defines as painting nothing
are removed from both sides before comparing. A name that shows nothing
at all is shown on the delete screens as "Wallet N", so it can still be
typed back.

Model: opus-5-5

README.md

@@ -1788,7 +1788,10 @@ view would leave a wallet one click from deletion.
       new password — and, in bold, that without that phrase written down the
       deletion loses everything the wallet holds, forever
     - That the other wallets are not touched
-    - The wallet's name, and a text input asking for it to be typed back
+    - The wallet's name, and a text input asking for it to be typed back. A name
+      that shows nothing at all (only spaces, or only characters that paint
+      nothing) is shown as "Wallet N", its position in the list, and that is
+      what is typed back.
     - Error line
     - "Delete This Wallet Forever" button
 - **Transitions**:
@@ -1796,9 +1799,9 @@ view would leave a wallet one click from deletion.
       outcomes as "Confirm Delete" above, through the same `finishDelete()`, so
       the selection repair, permission cleanup and `AUTISTMASK_ACTIVE_CHANGED`
       broadcast are identical on both routes
-    - "Delete This Wallet Forever" (name does not match) → "That is not the name
-      of this wallet. Type <name> to confirm." on the error line, nothing
-      deleted
+    - "Delete This Wallet Forever" (name does not match, or the field is empty)
+      → "That is not the name of this wallet. Type <name> to confirm." on
+      the error line, nothing deleted
     - "Back" → **DeleteWallet**, re-entered through its `show()` so the wallet
       selection comes back with it. The two delete screens are siblings rather
       than parent and child: nothing is pushed on the way here, so both have
@@ -1807,8 +1810,13 @@ view would leave a wallet one click from deletion.
   secret protects nobody: an attacker at the popup who wants the wallet gone can
   uninstall the extension, so the only person such a gate stops is the owner who
   forgot it. The typed name is a check that the user knows which wallet they are
-  on, not a secret, so it is matched with surrounding spaces and letter case
-  ignored.
+  on, not a secret, so it is matched as the user can see it: letter case,
+  surrounding spaces and repeated inner spaces are ignored, and characters that
+  paint nothing (format characters such as the zero-width space,
+  default-ignorable characters, and DELETE — the same set
+  `src/shared/symbolSpoof.js` strips) are removed from both sides before
+  comparing. An empty field, or one holding only spaces or such characters, is
+  refused whatever the wallet is called.
 - Not in `RESTORABLE_VIEWS`, alongside `delete-wallet-confirm`: a popup reopened
   by accident must not land on a screen whose button erases key material.