PLI: return the 7-byte location object, bound every proactive chain

The PLI answer used the 5-byte form 13 05 <MCC/MNC> <LAC> with LAC 0000
and no Cell ID.  That is the *Network Rejection event download* form
(TS 31.111 8.19.1); a PLI location for GERAN is 7 bytes - MCC/MNC, LAC
and Cell ID.  A card applet that re-reads its location (the Alfa
MultiIMSI applet, after a *LOCI status change) treated it as empty and
re-requested PLI on every STATUS tick.

The default is now 13 07 00F110 0001 0001: PLMN 001/01 (the test
network), LAC 0001, Cell ID 0001.  _build_tr injects it after the
Result; the TR data is pinned by a test.

While verifying a live PLI, the manual /api/status-poll chain turned
out to be unbounded: it looped on the PLI storm while holding
_CARD_LOCK, so the request never returned and every card operation
waited.  _handle_proactive_chain's max_rounds now defaults to
_POLL_CHAIN_MAX (the background poll always passed it; the manual poll,
ENVELOPE, menu and TP chains did not), and the manual poll passes it
explicitly.  A card that re-queues a command can no longer wedge the
card lock from any call site.

Tests: the PLI default + the built TR, the default chain bound and the
manual-poll call pin.  1061 Python + 1069 frontend; sw cache simple-v477.

frontend/help.html

@@ -539,7 +539,7 @@
 		<li><strong>06</strong> Access Technology &middot; <strong>08</strong> IMEISV &middot; <strong>09</strong> Search Mode</li>
 		<li><strong>0A</strong> Battery &middot; <strong>0E</strong> Multiple Access Technologies</li>
 	</ul>
-	<p class="text-sm mb-3">Values persist server-side until restart.  Sensible defaults are pre-settled for the qualifiers the ETSI specs define (location as the test network 001/01, the test IMEI 490154203237518 and its IMEISV, language &lsquo;en&rsquo;, E-UTRAN access technology, automatic search mode, a full battery): a value you set overrides its default, and <strong>clearing the field restores it</strong>; the date/time qualifier is answered from the host clock while empty, and the 3GPP/3GPP2-specific qualifiers (NMR, ESN, MEID, CSG/HNB, WLAN, slices, CAG, &hellip;) stay empty - the ETSI specs define no contents for them.  A field the server cannot use (a value that is not hex, an odd number of digits, a code outside the qualifier list) is named under the Save button instead of being silently dropped.  When the card issues PLI, the server injects the values into the TERMINAL RESPONSE - also into a test-script expectation's answer.</p>
+	<p class="text-sm mb-3">Values persist server-side until restart.  Sensible defaults are pre-settled for the qualifiers the ETSI specs define (location as the test network 001/01 with test LAC 0001 and Cell ID 0001 &mdash; the 7-byte PLI form, not the shorter Network Rejection one, the test IMEI 490154203237518 and its IMEISV, language &lsquo;en&rsquo;, E-UTRAN access technology, automatic search mode, a full battery): a value you set overrides its default, and <strong>clearing the field restores it</strong>; the date/time qualifier is answered from the host clock while empty, and the 3GPP/3GPP2-specific qualifiers (NMR, ESN, MEID, CSG/HNB, WLAN, slices, CAG, &hellip;) stay empty - the ETSI specs define no contents for them.  A field the server cannot use (a value that is not hex, an odd number of digits, a code outside the qualifier list) is named under the Save button instead of being silently dropped.  When the card issues PLI, the server injects the values into the TERMINAL RESPONSE - also into a test-script expectation's answer.</p>
 
 	<h3 id="network-simulation" class="text-lg font-medium mb-2">8.7 Network simulation</h3>
 	<p class="text-sm mb-2">Replays the write patterns a real phone performs when the network condition changes (trace study in <code class="font-mono text-sm">projects/UICC_NAA.md</code>): EPS attach, service loss / limited service, roaming denial, 2G fallback, SMS delivery, cell-broadcast reconfiguration and AUTHENTICATE. One button per scenario; the card must be equipped.</p>