fix: SCP80/RAM re-read the preset before every operation; no counter bump on a rejected send (v3.6.3)

The SCP80/RAM forms hold a copy of the preset (counter, keys, TAR, SPI).
Editing the preset on the Cards tab saved correctly, but the form kept the
old copy: the operation sent the stale counter (the card answers cntr_low)
and the post-send sync wrote the stale value back over the preset - the
saved counter silently reverted.  Reproduced in a real DOM:

  after select in SCP80:  preset=0000000001  sp=0000000001
  after Cards edit+save:  preset=00000000AA  sp=0000000001
  after a sync:           preset=0000000001  (edit lost)

- `cardsApply()` split into `cardsApplyFields()` (field copy, no packet) and
  `cardsApply()` = fields + genSp; new `spRefreshFromPreset(selId)` re-reads
  the selected preset from `sp-card-sel` / `ram-card-sel` and re-applies it.
- `pysimSendOta()` and `ramExecute()` call it before starting, so every
  SCP80/RAM operation uses the preset as it is now.
- A rejected send no longer advances the counter: new `spPorAccepted(por)`
  gates the advance+write-back in `pysimSendOta`, the Explore pagination and
  its GET DATA step, and the server's RAM install (`_ram_next_cntr`: advance
  only for `por_ok`/`no_por` steps).  A failed install still returns
  `final_cntr` (the accepted prefix) and the PWA persists it, so a retry
  never replays a counter the card already consumed.
- tests: cards_counter.test.js (the stale-form regression, RAM selector,
  fields-without-genSp, spPorAccepted) and `_ram_next_cntr` cases; the
  cards_form/ram harnesses updated for the split.
- docs/api.md counter semantics; AGENTS preset-source-of-truth rule.

607 frontend / 488 Python green; version 3.6.3; sw simple-v276.

frontend/tests/ram.test.js

@@ -45,6 +45,12 @@ const els = {};
 const doc = { getElementById: (id) => { if (!els[id]) els[id] = {value:''}; return els[id]; } };
 global.document = doc;
 
+// ramApplyCard/ramExecute delegate to the SP-form helpers; their real
+// behaviour (and the preset re-read before an operation) is covered by
+// cards_counter.test.js, so keep them as global stubs here.
+globalThis.cardsApply = () => {};
+globalThis.spRefreshFromPreset = () => '';
+
 function reset() { for (const id of Object.keys(els)) delete els[id]; }
 
 function genRamResult(fields) {
@@ -330,7 +336,8 @@ test('ramApplyCard remembers a valid picked preset', () => {
 	ramApplyCard('');
 	assert.strictEqual(_ramCardIdx, 1, 'invalid pick must not forget the preset');
 	delete globalThis.cards;
-	delete globalThis.cardsApply;
+	globalThis.cardsApply = () => {};
+	delete globalThis.cards;
 });
 
 test('ramExecute commits the dropdown selection before running', async () => {