fix(ux): plain-language, actionable user-facing messages (core)

Squashed integration of the user-facing message audit for this surface set.
Full per-finding receipts: /tmp/ux-audit/lanes/*-receipt.md (campaign artifacts).

tools/browser_vault_tool.py

@@ -557,7 +557,7 @@ def _confirm_payment_fill(label: str, origin: str) -> bool:
         f"Fill payment card '{label}' on {origin}",
         "The agent wants to enter your saved card details into this checkout page. The card number and "
         "CVC never enter the conversation. Approve only if you intend to pay here.",
-        surface="vault-payment") == "accept"
+        surface="vault-payment", title="Confirm payment card fill?") == "accept"
 
 
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