[DOC] pos_payment_method_cashdro_fix: the console check it describes is not possible

The manual check told the reader to tell two fixes apart by the browser
console, but the `catch` of the base module has no error binding and never
logs: following it shows an empty console, which is exactly why the current
failure could not be diagnosed on site.

Point at pos_payment_method_cashdro_flow_fix instead, which makes the errors
visible and covers the payment flow these three fixes do not.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

pos_payment_method_cashdro_fix/README.rst

@@ -51,10 +51,12 @@ To check the three fixes on a PoS with a CashDro terminal:
    due amount (fix 2).
 #. The drawer must start the operation and ask for the amount, instead of the
    *"An error occurred while connecting to the cashdro"* dialog (fixes 1 and 3).
-#. With no CashDro at hand, the browser console tells fix 1 from fix 3 apart:
-   without this module the failure is a ``TypeError: Cannot read properties of
-   undefined (reading 'payment_method')``; with it, a network error against the
-   configured host.
+
+These three fixes are not enough on their own: the payment flow of the base
+module is broken on 18.0 for reasons of its own, and it hides every failure —
+these ones included — behind that same dialog, without logging anything.
+Install ``pos_payment_method_cashdro_flow_fix`` as well; its ``USAGE`` explains
+how to read what actually went wrong.
 
 The Python side is covered by the tests. The base module lives outside this
 repo, so the OCA sources have to be on the addons path (mounted by
@@ -76,7 +78,7 @@ the credential fields that are missing from the loader, and the JavaScript
 patches are idempotent with respect to the fixed upstream code.
 
 The JavaScript side can't be covered by automated tests, as it needs a CashDro
-terminal answering on the network.
+terminal answering on the network. See ``USAGE`` for the manual check.
 
 Contributors
 ============