v3.14.2: the counter probe's verdict rule

The ladder only advances on cntr_low; any other verdict stops the search.
A stop on a non-por_ok verdict after at least one cntr_low keeps the value
anyway - the earlier rejection proves it is above the card's counter - but
the response reports success: false with counter_saved, the verdict and the
saved counter ("something is likely wrong with the security settings");
the PWA shows it amber.  Without a prior cntr_low nothing is saved, and a
missing PoR stays an error.  actual_response_sms_submit/ussd count as
accepted.

Docs: docs/api.md, repo AGENTS.  sw cache simple-v377.
Tests: 672 Python + 798 frontend green.

frontend/tests/ram.test.js

@@ -983,6 +983,8 @@ test('every SCP80/RAM flow checks the low counter and stops', () => {
 	assert.ok(sync.includes('spKeysetSync()'), 'the keyset labels must refresh');
 	assert.ok(sync.includes("ramListingSpi2('40')"),
 		'the RAM view must probe with the RAM listing transport (a PoR is required)');
+	assert.ok(sync.includes('data.counter_saved'),
+		'the saved-on-error case must be reported in amber');
 });
 
 test('the RAM form offers the command format choice', () => {