docs: README matches ConfirmTx's wrong-password message and fee-bound refusal (closes #610)

ConfirmTx shows "That password is incorrect. Please try again." for a
wrong password, as every other screen that asks for one does. README
quoted "Wrong password." instead.

The fee-bound refusal said the RPC endpoint always fills in the gas
limit and fees at signing. An ETH amount that Max filled in is signed
with the gas limit and fees of the screen's own fee estimate instead.
README now says so, and lists what assertWithinCeilings() checks.

Model: opus-5-5

README.md

@@ -2053,15 +2053,21 @@ view would leave a wallet one click from deletion.
       fee estimate and the contract and never-sent recipient checks ask that
       network's RPC endpoint, and the Etherscan label check asks that network's
       explorer
-    - "Sign & Send" (correct password) when the gas limit, a fee per gas or the
-      total fee the RPC endpoint fills in at signing is over its bound in
-      `assertWithinCeilings()` (`src/shared/approvalVerify.js`) → nothing is
-      signed; "The gas limit or fee the RPC endpoint quoted for this transaction
-      is more than this wallet will sign for, so it was not sent. Please go back
-      and try again." in its own box, the same sentence for all three, no screen
-      change
-    - "Sign & Send" (wrong password) → "Wrong password." on the password error
-      line, no screen change
+    - "Sign & Send" (correct password) when the gas limit or a fee is over its
+      bound → nothing is signed; "The gas limit or fee the RPC endpoint quoted
+      for this transaction is more than this wallet will sign for, so it was not
+      sent. Please go back and try again." in its own box, no screen change. For
+      an ETH amount that Send's "Max" filled in, the gas limit and fees are
+      those of this screen's own fee estimate (see Amount above). For any other
+      send, the RPC endpoint fills in the gas limit and fees at signing. Just
+      before signing, `assertWithinCeilings()` (`src/shared/approvalVerify.js`)
+      refuses the send when any of these is over its bound:
+        - the gas limit
+        - each fee per gas the transaction sets
+        - the total fee: the gas limit times `maxFeePerGas`, or times `gasPrice`
+          when the transaction has no `maxFeePerGas`
+    - "Sign & Send" (wrong password) → "That password is incorrect. Please try
+      again." on the password error line, no screen change
     - "Sign & Send" signs as the From address above, not as whichever address is
       selected: the two are saved separately, so the popup can reopen onto this
       screen with another address selected. When the selected wallet does not