scp81: always reuse the connection, collapsible options, label polish (v2.2.15)

- Keep-alive is no longer a setting: the TLS connection stays open between
  POSTs for the whole dialog (the card, as HTTP client, may still dial a new
  one at any time - GP Am. B 4.3.1) and only the 204 ends it, with a clean
  close_notify while the response is still buffered, then FIN. Dropped
  keep_alive/on_before_close/_scp81_wait_drained and the Connection-header
  'close' value (the API, status and UI no longer carry a keep-alive knob).
- The Listener Options block is a collapsed <details> with a 'custom' badge
  when anything differs from the reference defaults; the Reset button moved
  into the body so it cannot toggle the panel.
- X-Admin-Targeted-Application is opt-in (checkbox + //aid/... field, field
  disabled while off); X-Admin-Next-URI has a checkbox + hint explaining the
  one-shot rule of GP Am. B 4.4.2; both dependent fields grey out when
  unchecked.
- Labels/i18n: 'Chunked body (Transfer-Encoding: chunked)' stays English,
  'Show link events (...)', 'Теги comprehension-required'; the compact-header
  wording now spells out that it omits the optional space after ':' (legal
  per RFC 7230 3.2 OWS; saves one byte per header).
- Tests: a 200 keeps the socket for the next POST; the 204 closes with a
  mutual close_notify exchange; options helper/badge unit tests; removed the
  close-per-response and drain-wait tests. SW cache otaman-v181.

frontend/help.html

@@ -327,7 +327,7 @@
 		<li><strong>Pass-through (card destination)</strong> — no listener and no target: the terminal connects each BIP channel to the destination the card requests in OPEN CHANNEL (Other address + Transport level port, TCP client remote only; the specs define no default port, so an incomplete request fails the channel). TLS is terminated by that platform, and the server's network is used (lab only).</li>
 		<li><strong>Capture (dump)</strong> — accepts the card's TCP channel and logs whatever it sends (e.g. the TLS ClientHello) without answering.</li>
 	</ul>
-	<p class="mb-2">The <strong>Options</strong> block (applied at <strong>Start</strong>, remembered in the browser) exposes the HTTP framing &mdash; <strong>chunked</strong> body / <strong>chunk size</strong> (0 = the whole response in one TLS record), keep-alive, the Connection header, compact headers and the Next-URI (unchecked = omit the header) &mdash; and the script framing (indefinite <code class="font-mono text-sm">AE 80 …</code> / definite <code class="font-mono text-sm">AA</code> Command Scripting template, comprehension-required tags, targeted application). <strong>Link events</strong> (Channel status ENVELOPEs, TS 102 223 &sect;7.5.11) apply to every mode. TLS itself has no settings: the listener offers TLS 1.0&ndash;1.2 and all PSK suites and lets the card negotiate; the state line and the TLS log show the version/cipher actually used, and a handshake that fails for a TLS/cipher reason is logged as <code class="font-mono text-sm">tls-handshake-failed</code>.</p>
+	<p class="mb-2">The <strong>Options</strong> block (collapsed by default; a <em>custom</em> marker appears when anything differs from the reference defaults; applied at <strong>Start</strong>, remembered in the browser) exposes the HTTP framing &mdash; <strong>Chunked body</strong> / <strong>chunk size</strong> (0 = the whole response in one TLS record), the Connection header, compact headers (omitting the optional space after <code class="font-mono text-sm">:</code>, legal per RFC 7230 &sect;3.2) and the Next-URI (checkbox + template; unchecked = one-shot: the card executes the command, returns no response string and closes the session) &mdash; and the script framing (indefinite <code class="font-mono text-sm">AE 80 …</code> / definite <code class="font-mono text-sm">AA</code> Command Scripting template, comprehension-required tags, and the optional <code class="font-mono text-sm">X-Admin-Targeted-Application</code> with its own checkbox). <strong>Show link events</strong> (Channel status ENVELOPEs, TS 102 223 &sect;7.5.11) applies to every mode. The connection is kept open between POSTs and closed cleanly at the 204. TLS itself has no settings: the listener offers TLS 1.0&ndash;1.2 and all PSK suites and lets the card negotiate; the state line and the TLS log show the version/cipher actually used, and a handshake that fails for a TLS/cipher reason is logged as <code class="font-mono text-sm">tls-handshake-failed</code>.</p>
 	<p class="mb-2"><strong>Script</strong> selects the command list served over the session — <strong>None</strong> (leave the server's configured script) or one of the scripts from the <strong>Scripts</strong> pill; the chosen list is sent to the server when the listener starts.</p>
 	<p class="text-sm mb-3">The state line shows the listener, the negotiated identity and live channels (bytes in/out). <strong>Script results (R-APDUs)</strong> lists each served C-APDU with its R-APDU/SW and a <em>done/total</em> progress; the <strong>HTTP OTA log</strong> records OPEN/CLOSE CHANNEL, SEND/RECEIVE DATA and every TLS/HTTP/script step (<code class="font-mono text-sm">tls-handshake</code>, <code class="font-mono text-sm">tls-request</code>, <code class="font-mono text-sm">script-send</code>, <code class="font-mono text-sm">script-rapdu</code>, <code class="font-mono text-sm">script-page</code>, <code class="font-mono text-sm">script-done</code>, <code class="font-mono text-sm">data-available</code>, <code class="font-mono text-sm">peer-close</code>), with <strong>Clear</strong>.</p>
 	<h3 id="scp81-scripts" class="text-lg font-medium mb-2">5.2 Scripts</h3>