docs: fix stale zero claim, list what decoded approval amount lines read (closes #369)

The README said a genuine zero always renders `0.0000`, beside a
`Min. received` example, though a zero minimum there now reads
`None (no minimum guaranteed)`. It now says the amount rule renders a
zero as `0.0000` and that two swap lines say a zero in words instead:
`Min. received` for a zero minimum, and `Amount` when it shows a V4
exact-in `amountIn` of zero.

A new list says what the decoded ERC-20 and swap amount lines on the
transaction approval screen can read, including that a zero
`BALANCE_CHECK_ERC20` `minBalance` now reads the no-minimum wording.
The token permission warning on the signature screen is left to the
SignApproval section.

Model: opus-5-5

TODO.md

@@ -173,6 +173,20 @@ but the review is broader than any of them.
   standalone storage entry, never part of the versioned `autistmask` profile, so
   the state schema is untouched and no existing profile is affected.
 
+- 2026-09-21: `README.md` no longer says a genuine zero always renders `0.0000`
+  ([#369](https://git.eeqj.de/sneak/AutistMask/issues/369)). The amount rule
+  still renders one as `0.0000`, but two swap lines say a zero in words instead:
+  `Min. received` reads `None (no minimum guaranteed)` for a zero minimum, and
+  `Amount` reads `All available (V4 open delta)` when the amount it shows is a
+  V4 exact-in `amountIn` of zero. A new list says what the decoded ERC-20 and
+  swap amount lines on the transaction approval screen can read: a formatted
+  quantity, base units with decimals unknown, `Unlimited`,
+  `All available (V4 open delta)` and `None (no minimum guaranteed)`, which a
+  zero `minBalance` on a `BALANCE_CHECK_ERC20` step now reads instead of
+  `0.0000` at a known scale. The README also names
+  `Unknown (not named in the calldata)` on the swap's token lines, and points to
+  SignApproval for the token permission warning's own wording. Docs only.
+
 - 2026-08-30: An address no longer wraps, or is shortened to fit, in any of the
   common views ([#380](https://git.eeqj.de/sneak/AutistMask/issues/380)). The
   wallet list was the reported case: the address shared one row with the