v3.20.0: the server-owned SCP80 counter (an untouched field = the preset's next value)

The counter an operation consumed was re-entered by the PWA on every send
(the form field was filled from the preset and posted back), so a stale tab
could send a value the card rejects (cntr_low), and typing in the field
silently wrote the preset.  Now the store is the single source of truth and
the form field is a per-send override (Option B).

- _preset_counter_seed: an explicit `cntr` in the request wins (a hand send,
  the counter probe or a pre-built packet may deliberately pick one);
  otherwise the preset store's value for the packet's keyset.  Wired into
  /api/send-ota (the APDU path; the pre-built `sp` path keeps the caller's
  bookkeeping value - the packet carries its own counter), /api/ram-install,
  /api/ram-install-app, /api/cap-compat, /api/tar-probe and /api/sp-verify
  (the reference must use the counter the JS packet was built with).
- the send-ota response echoes the effective `cntr` (a caller that omitted
  one learns what was used) and the OTA SEND log line prints it.
- persistence is unchanged and monotonic (presets.set_counter refuses
  backwards writes), pinned by tests: an explicit lower counter is used for
  the packet but never lowers the store, a higher accepted one is saved.
- PWA: the Secured packet counter field starts empty with the preset's next
  value as its placeholder (auto: <cntr>); typing affects that send only and
  is never written to the preset (spCntrSyncPreset is gone), spParams /
  getRamSpParams omit an empty counter, the RAM/send flows sync only the
  local preset copy (forward-only) instead of filling the field, the +/-
  buttons start from the effective value, and the preview/verify packet is
  built from the effective counter (genSp).  Placeholder translated EN/RU.
- the runner and /api/counter-probe keep their existing seeding (the probe
  already starts at the failed value and walks above it).
- docs: api.md's optional-`cntr` contract + seeding notes on every endpoint,
  help EN/RU 3.1.  Tests: 822 frontend + 734 Python; sw cache simple-v393.

frontend/tests/cards_counter.test.js

@@ -31,6 +31,8 @@ let code = '';
 for (const fn of ['cardsTarList', 'cardsRoleDefault', 'cardsRoleTar',
 	'cardsTarEntry', 'cardsTarMsl', 'cardsApplyFields', 'cardsApply',
 	'spRefreshFromPreset', 'spPorAccepted', 'spNextCntr', 'spPresetIdx',
+	'spPresetCounterValue', 'spCntrPlaceholder', 'spCntrEffective', 'spCntrAhead',
+	'spCntrAdjust',
 	'spKeysetKvnOf', 'spKeysetList', 'spKeysetFor', 'spKeysetCheck',
 	'spKeysetOptionsHtml', 'cardsKeysetRowHtml', 'cardsKeysetRowsRender',
 	'cardsKeysetAdd', 'cardsKeysetRemove', 'cardsKeysetKvnUpdate',
@@ -51,6 +53,7 @@ eval(code);
 globalThis._genSpBuild = () => {};
 globalThis.spShowSizeInfo = () => {};
 globalThis.spKeysetSync = globalThis.spKeysetSync || (() => {});
+globalThis.t = s => s;
 
 // The SP form is a working copy: the preset is the source of truth, and
 // every SCP80/RAM operation re-reads it before starting (v3.6.3).  The plain
@@ -81,16 +84,23 @@ function fakeEnv(selValue, selId, presetCntr) {
 	return { els, gen: () => gen };
 }
 
-test('spRefreshFromPreset re-reads the edited preset before an operation', () => {
+test('spRefreshFromPreset keeps an explicit counter override, empty = auto', () => {
 	const env = fakeEnv('0', 'sp-card-sel', '00000000AA');
-	env.els['sp-cntr'].value = '0000000001';        // stale form copy
+	env.els['sp-cntr'].value = '0000000001';        // explicit override
 	assert.strictEqual(spRefreshFromPreset('sp-card-sel'), '00000000AA');
-	assert.strictEqual(env.els['sp-cntr'].value, '00000000AA');
-	assert.ok(env.gen() > 0, 'the packet must be regenerated from the new counter');
+	assert.strictEqual(env.els['sp-cntr'].value, '0000000001',
+		'a typed counter survives the pre-send refresh');
+	assert.ok(env.gen() > 0, 'the packet must be regenerated from the preset');
+	// an empty field means "auto": the server seeds the counter, and the
+	// preset's next value is shown as the placeholder (v3.20.0)
+	env.els['sp-cntr'].value = '';
+	spRefreshFromPreset('sp-card-sel');
+	assert.strictEqual(env.els['sp-cntr'].value, '');
+	assert.match(env.els['sp-cntr'].placeholder, /00000000AA/);
 	// no preset selected: the manual form is left alone
 	globalThis.cards = [];
 	assert.strictEqual(spRefreshFromPreset('sp-card-sel'), '');
-	assert.strictEqual(env.els['sp-cntr'].value, '00000000AA');
+	assert.strictEqual(env.els['sp-cntr'].value, '');
 });
 
 test('spRefreshFromPreset for the RAM selector targets the ISD TAR', () => {
@@ -105,23 +115,34 @@ test('the pre-send refresh keeps a hand-edited packet TAR (v3.6.21)', () => {
 	env.els['sp-tar'].value = 'AF4D01';   // e.g. a push/link trigger target
 	assert.strictEqual(spRefreshFromPreset('sp-card-sel', true), '0000000020');
 	assert.strictEqual(env.els['sp-tar'].value, 'AF4D01', 'the typed TAR must survive the send');
-	assert.strictEqual(env.els['sp-cntr'].value, '0000000020', 'the counter still refreshes');
+	assert.strictEqual(env.els['sp-cntr'].value, '', 'the counter field stays an override');
+	assert.match(env.els['sp-cntr'].placeholder, /0000000020/);
 	// an explicit preset apply (or a pack) still sets the TAR
 	cardsApplyFields(0);
 	assert.strictEqual(env.els['sp-tar'].value, 'B00000');
 });
 
-test('cardsApplyFields fills the form without generating a packet', () => {
+test('cardsApplyFields leaves the counter to the server (auto) and shows it as a placeholder', () => {
 	const env = fakeEnv('0', 'sp-card-sel', '0000000007');
-	env.els['sp-cntr'].value = 'nonsense';
+	env.els['sp-cntr'].value = 'nonsense';          // an old override
 	assert.strictEqual(cardsApplyFields(0), true);
-	assert.strictEqual(env.els['sp-cntr'].value, '0000000007');
+	assert.strictEqual(env.els['sp-cntr'].value, '',
+		'applying a preset clears the override (empty = the server seeds it)');
+	assert.match(env.els['sp-cntr'].placeholder, /0000000007/);
 	assert.strictEqual(env.gen(), 0, 'a plain field refresh must not rebuild the packet');
 	cardsApply(0);
 	assert.strictEqual(env.gen(), 1);
 	assert.strictEqual(cardsApplyFields(3), false);
 });
 
+test('the counter +/- buttons start from the preset value and create an override', () => {
+	const env = fakeEnv('0', 'sp-card-sel', '0000000020');
+	spCntrAdjust(1);
+	assert.strictEqual(env.els['sp-cntr'].value, '0000000021');
+	spCntrAdjust(-1);
+	assert.strictEqual(env.els['sp-cntr'].value, '0000000020');
+});
+
 test('spPorAccepted treats a missing PoR and por_ok as accepted', () => {
 	assert.strictEqual(spPorAccepted(undefined), true);
 	assert.strictEqual(spPorAccepted({ response_status: 'por_ok' }), true);