fix: give a wallet whose password is lost a way out, and say the password cannot be reset (closes #312)

A user who forgot their password but held their recovery phrase was permanently
locked out: deletion was password-gated and re-importing the phrase was refused
as a duplicate. Their only escape was destroying extension storage through
browser internals, taking every other wallet with it.

DeleteWallet gains an "I have lost my password" route that destroys the stored
secret after the wallet's name is typed back. No password gate was added:
requiring one to discard a secret protects nothing, since an attacker who wants
destruction can uninstall the extension, and the only person it stops is the
legitimate user who lost it. The screen is excluded from RESTORABLE_VIEWS and
registers an onViewLeave cleanup.

Deletion was chosen over re-import because a key wallet is duplicate-checked by
address rather than xpub, so an xpub-only relaxation would leave that user
still wedged; because re-import makes the user retype their recovery phrase
into a live popup merely to change a password; and because it reaches no end
state that delete-then-import plus scanForAddresses() does not. The attacker
argument did not decide it — re-import clears the "no worse than the phrase
alone" bar.

All three AddWallet password hints now state the password cannot be recovered
or reset and name that mode's only backup, the xprv mode correctly claiming no
recovery phrase. deleteAddress.js no longer tells the user that deleting a
wallet asks for a password, which this change made false.

The typed confirmation collapses internal whitespace on both sides: a wallet
renamed with two spaces displays with one, so the string a user could see and
type could never match, making the confirmation untypable on the one screen
whose purpose is un-wedging a stuck user.

Measured, not reasoned, after review found the first reserve twice too large
and pushing the Import button below the fold: #btn-add-wallet-confirm bottom
628.13 -> 580.13 at 360x600, scrollHeight 636 -> 600, hint box 48px identical
across all three tabs and on re-entry. make check 40 suites / 828 tests,
test-e2e 55/55, test-e2e-firefox 8/8.

src/popup/views/addWallet.js

@@ -42,12 +42,24 @@ let currentMode = "mnemonic";
 
 const MODES = ["mnemonic", "privkey", "xprv"];
 
+// Each hint names what this import mode's own backup is, because a key
+// wallet and an xprv wallet have no recovery phrase to point the user at.
+// All three say the same thing about the password: it is gone for good if
+// it is forgotten. That sentence is the only warning the user gets before
+// the wallet exists, and without it the lost-password route in
+// views/deleteWallet.js is the first they hear of it.
+//
+// Keep the three within a couple of characters of each other in length.
+// The hint sits directly above the password fields and the tabs swap it in
+// place, so a wording that wraps to a different number of lines would move
+// those fields under the pointer; the reserved height on
+// #add-wallet-password-hint is the other half of that guarantee.
 const PASSWORD_HINTS = {
     mnemonic:
-        "This password encrypts your recovery phrase on this device. You will need it to send funds.",
+        "This password encrypts your recovery phrase on this device. You will need it to send funds. It cannot be recovered or reset, so keep your recovery phrase written down: it is the only backup of this wallet.",
     privkey:
-        "This password encrypts your private key on this device. You will need it to send funds.",
-    xprv: "This password encrypts your key on this device. You will need it to send funds.",
+        "This password encrypts your private key on this device. You will need it to send funds. It cannot be recovered or reset, so keep your private key saved somewhere safe: it is the only backup of this wallet.",
+    xprv: "This password encrypts your key on this device. You will need it to send funds. It cannot be recovered or reset, so keep your extended private key saved somewhere safe: it is the only backup of this wallet.",
 };
 
 function switchMode(mode) {