Landing page: add PM_X-1 Explorer pane

Adds the Explorer to index.html's VERSIONS list between the Kit and Teacher
panes. file: "/info-explorer.html" since there's no explorer.html widget yet;
the existing replace("/", "/info-") logic is wrapped in an idempotent infoOf()
helper so "Specs & info" doesn't double-prefix it.

info-explorer.html also gets the standard ?embed=1 handler (matches every
other info-*.html), so the landing-page iframe preview strips chrome + auto-
sizes when the pane is selected.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

index.html

@@ -139,12 +139,16 @@ const SAMPLES = {}; let state = { bpm:120, volume:0.85 }, meters = [], muteWindo
 const VERSIONS = [
   { key:"editor",   file:"/editor.html",  name:"PM_E‑1 Editor",   chip:"app", h:620, sum:"Design grooves: stack meter lanes, per‑step accents/ghosts/mutes, swing & polyrhythm, set lists, per‑lane dB gain." },
   { key:"kit",      file:"/kit.html",     name:"PM_K‑1 Kit",      chip:"hw",  h:560, sum:"Build it today — a Raspberry Pi Pico on the 52Pi touchscreen kit; tap the 3.5″ screen, joystick tempo, RGB beat light, buzzer. MicroPython firmware included." },
+  { key:"explorer", file:"/info-explorer.html", name:"PM_X‑1 Explorer", chip:"hw",  h:560, sum:"Off‑the‑shelf — the Pimoroni Explorer (RP2350, 2.8″ LCD, 6 buttons, piezo) as a button‑driven sibling to the Kit. Edit on the web with Live sync; the device mirrors play/stop/tempo/track changes both ways." },
   { key:"teacher",  file:"/teacher.html", name:"PM_T‑1 Teacher",  chip:"hw",  h:440, sum:"Studio / lesson desk console — colour TFT of every lane, arcade buttons, instrument pass‑through." },
   { key:"stage",    file:"/stage.html",   name:"PM_S‑1 Stage",    chip:"hw",  h:430, sum:"Live foot pedal — two footswitches, expression‑pedal tempo, a big floor‑readable RGB beat light." },
   { key:"micro",    file:"/micro.html",   name:"PM_P‑1 Practice",    chip:"hw",  h:240, sum:"Inline practice bar — clickable thumb‑roller, amber 14‑segment, instrument in/out pass‑through." },
   { key:"showcase", file:"/showcase.html",name:"PM_D‑1 Display", chip:"hw",  h:540, sum:"Pyramid display piece — an RGB‑light pendulum combining every lane's subdivisions & accents." },
   { key:"initial",  file:"/player.html",  name:"PM_C‑1 Concept",  chip:"",    h:440, sum:"The idealized concept render — full multi‑lane display and set‑list navigation." },
 ];
+// "Specs & info" link helper - usually swaps /<dev>.html for /info-<dev>.html, but if the
+// pane already POINTS at the info page (PM_X-1 has no separate widget yet), keep it as is.
+const infoOf = (f) => f.startsWith("/info-") ? f : f.replace("/", "/info-");
 const DEFAULT_PROG = (typeof SEED_SETLISTS !== "undefined" && SEED_SETLISTS[0] && SEED_SETLISTS[0].items[0] && SEED_SETLISTS[0].items[0][1]) || "v1;t120;kick:4;snare:4=.X.X;hat:4/2";
 
 let cur = "editor", userEditing = false;
@@ -158,7 +162,7 @@ function renderPanes() {
       <p>${v.sum}</p>
       <div class="links">
         <a class="open" href="${v.file}" target="_blank" rel="noopener" onclick="event.stopPropagation()">Open ↗</a>
-        <a class="open" href="${v.file.replace("/", "/info-")}" target="_blank" rel="noopener" onclick="event.stopPropagation()">Specs &amp; info ⓘ</a>
+        <a class="open" href="${infoOf(v.file)}" target="_blank" rel="noopener" onclick="event.stopPropagation()">Specs &amp; info ⓘ</a>
       </div>
     </div>`).join("");
   $("panes").querySelectorAll(".pane").forEach((el) => {
@@ -172,7 +176,7 @@ function loadVersion(key, prog) {
   $("panes").querySelectorAll(".pane").forEach((p) => p.classList.toggle("active", p.dataset.key === key));
   $("vpName").innerHTML = "<b>" + v.name + "</b>";
   $("vpOpen").href = v.file;
-  $("vpInfo").href = v.file.replace("/", "/info-");
+  $("vpInfo").href = infoOf(v.file);
   vp.style.height = (v.h || 440) + "px";
   vp.src = v.file + "?embed=1" + (prog ? "#p=" + encodeURIComponent(prog) : "");
   if (prog && !userEditing) box.value = prog;

info-explorer.html

@@ -6,6 +6,14 @@
 <title>VARASYS PM_X-1 Explorer - wiring, parts &amp; firmware (Pimoroni Explorer / RP2350)</title>
 <meta name="description" content="PM_X-1 Explorer - the Pimoroni Explorer (PIM744, RP2350) as a 6-button polymeter metronome with live-sync to the web editor. Pinout, parts list, and the precompiled CircuitPython firmware bundle." />
 <link rel="icon" type="image/svg+xml" href="data:image/svg+xml;base64,@BUILD:favicon@">
+<script>
+  /* ?embed=1 -> strip site chrome (base.css [data-embed]) + auto-size to the host iframe */
+  (function(){ if(!/[?&]embed=1/.test(location.search)) return;
+    document.documentElement.dataset.embed="1";
+    function ph(){ try{ parent.postMessage({type:"varasys-h",h:Math.ceil(document.documentElement.getBoundingClientRect().height)},"*"); }catch(e){} }
+    addEventListener("load",ph); addEventListener("resize",ph); setTimeout(ph,300); setTimeout(ph,1000);
+  })();
+</script>
 <script>
   (function(){ try{ var p = localStorage.getItem("metronome.theme");
     if (p!=="light" && p!=="dark" && p!=="system") p = "system";