v3.24.0 review: the ARR fetch retry and the DF-scope note

- pysimArrEnsure no longer caches a transient /api/arr fetch failure:
  the next file click retries instead of silently showing no ARR rules
  for the rest of the card session (a success is still cached per
  session, and a session change refetches).
- The help (EN/RU) and both AGENTS state the cache scope: only the MF
  (2F06) and ADF.USIM (6F06) ARR copies are read - a reference to
  another DF's copy is left unresolved.
- Test: the transient failure retries, a success is cached, a session
  change refetches.  869 frontend + 856 Python; sw cache simple-v423.

frontend/index.html

@@ -15095,7 +15095,8 @@ async function pysimArrEnsure() {
 		const data = await pysimFetch('/api/arr');
 		_pysimArrCache = { session: _pysimCardSession, arrs: (data && data.arrs) || [] };
 	} catch (e) {
-		_pysimArrCache = { session: _pysimCardSession, arrs: [] };
+		// a transient fetch failure is not cached: the next click retries
+		return [];
 	}
 	return _pysimArrCache.arrs;
 }