Read the partner's identity out of master.conf instead of asking for it again

Plugin/unraid/pages/setup.php

@@ -38,6 +38,38 @@
 // master.conf pull (for partner servers) lives in the checklist, not here.
 
 $detectedHostname = vv_get_hostname();
+
+// ── Identity already on disk? ────────────────────────────────────────────────────────────────
+// A partner that has been sent the owner's master.conf already knows everything this step asks
+// for: the conf names the primary, and it names this machine in one of the HOSTn slots. Asking
+// for it again invites a typo in the one field the form itself warns is case-sensitive, and the
+// answer is sitting in a file two lines away.
+//
+// Only a *populated* conf counts. The installer seeds master.conf from the template, where every
+// HOSTn is empty — that is a fresh node with no identity, not a detected one.
+//
+// Matching is exact and case-insensitive, never a prefix: two hosts called Tower and Tower2 must
+// not resolve to each other, and there is no ambiguity to tolerate when the value was written by
+// the very host it names.
+$vvDetected = ['slot' => '', 'primary' => '', 'role' => ''];
+$vvMasterRaw = vv_read_conf_raw('master.conf');
+if ($vvMasterRaw !== '' && $detectedHostname !== '') {
+    preg_match_all('/^\s*(HOST\d+)\s*=\s*"([^"]*)"/m', $vvMasterRaw, $vvHm, PREG_SET_ORDER);
+    $vvSlots = [];
+    foreach ($vvHm as $m) {
+        $val = trim($m[2]);
+        if ($val !== '') $vvSlots[strtolower($m[1])] = $val;
+    }
+    foreach ($vvSlots as $slot => $name) {
+        if (strcasecmp($name, $detectedHostname) === 0) {
+            $vvDetected['slot'] = $slot;
+            $vvDetected['role'] = ($slot === 'host1') ? 'primary' : 'partner';
+            break;
+        }
+    }
+    // The primary is whatever HOST1 says, and it is only useful to a host that is not HOST1.
+    if ($vvDetected['role'] === 'partner') $vvDetected['primary'] = $vvSlots['host1'] ?? '';
+}
 ?>
 <link rel="stylesheet" href="/plugins/varaverk/css/varaverk.css">
 <style>
@@ -251,8 +283,14 @@ function vvSetStorage(mode) {
       vvSetStorage(d.mode);
       const hf = document.getElementById('vv-hostname');
       if (hf && !hf.value.trim()) hf.value = d.hostname;
+      // After the banner is rebuilt, never before — this appends to it, and the line above
+      // replaces its innerHTML wholesale.
+      vvApplyDetectedIdentity();
     }).catch(() => {
       document.getElementById('vv-detect-banner').innerHTML = '<span style="color:#444">Detection unavailable</span>';
+      // Identity comes off the local conf, not from the probe, so it still applies when the
+      // environment probe is the thing that failed.
+      vvApplyDetectedIdentity();
     });
 })();
 
@@ -266,6 +304,38 @@ function vvSetRole(role) {
   document.getElementById('vv-cond-partner')?.classList.toggle('show', role === 'partner');
 }
 
+// ── Identity detected from master.conf ────────────────────────────────────────
+// Applied, not enforced. Every field stays editable: the conf is evidence of what the owner
+// intended, and if it is wrong the person standing at the machine is the one who can say so.
+// What this removes is the need to retype three values that are already known — including the
+// hostname field whose own hint warns it is case-sensitive.
+const vvDetectedIdentity = <?= json_encode($vvDetected) ?>;
+
+function vvApplyDetectedIdentity() {
+  const d = vvDetectedIdentity;
+  if (!d || !d.slot) return;
+
+  vvSetRole(d.role);
+  if (d.role === 'partner') {
+    const pn = document.getElementById('vv-primary-hostname');
+    if (pn && d.primary) pn.value = d.primary;
+    const sel = document.getElementById('vv-partner-slot');
+    if (sel && [...sel.options].some(o => o.value === d.slot)) sel.value = d.slot;
+  }
+
+  const banner = document.getElementById('vv-detect-banner');
+  if (banner) {
+    const note = document.createElement('div');
+    note.style.cssText = 'margin-top:8px;padding:7px 10px;border-radius:3px;background:#0d1f0d;'
+                       + 'border:1px solid #1a3a1a;color:#4caf50;font-size:11px;line-height:1.5;';
+    note.textContent = d.role === 'partner'
+      ? `Identity read from master.conf — this server is ${d.slot.toUpperCase()}, joining `
+        + `${d.primary}. Change anything below if that is wrong.`
+      : 'Identity read from master.conf — this server is HOST1, the primary.';
+    banner.appendChild(note);
+  }
+}
+
 // ── Helpers ───────────────────────────────────────────────────────────────────
 function vvSetStatus(msg, cls) {
   const s = document.getElementById('vv-status');