v3.19.1: the compact-PoR decode guard (applet TAR responses reported as data)

pySim's CompactRemoteResp was applied to every response packet, so a
third-party applet's own TAR response parsed as count=128/SW=0110/data=''
(live 2026-10-04: the alfa-dsa applet's `80 01 10`) - a fabricated status
word and a lost response.

_decode_por now takes the plaintext command script's length (cmd_len): the
compact structure's command count cannot exceed it (TS 102 226 5.1.2
Table 5.1 - each command needs at least one byte), so a larger count is
classified `response_type: 'raw'`, the secured data becomes
`decoded.last_response_data` (a por.data check matches it) and no SW is
decoded; `secured_data` is exposed in every case.

Callers pass cmd_len where they know the plaintext: the test runner's scp80
step (None for a pre-built packet; carried in ctx['last_scp80'] for the
submit-PoR path), /api/send-ota (both paths), the RAM step sender and the
counter probe; a caller without it keeps the previous parse.

Docs: test-scripts.md and api.md describe the raw fallback.
Tests: 821 frontend + 729 Python; sw cache simple-v390.

frontend/index.html

@@ -1877,7 +1877,7 @@
 // ===== Version =====
 // Single source of truth for the PWA version: shown in the header and used
 // by the server version check in pysimConnect().
-const SIMPLE_VERSION = '3.19.0';
+const SIMPLE_VERSION = '3.19.1';
 document.getElementById('app-version').textContent = 'v' + SIMPLE_VERSION;
 
 // ===== Tab switching =====