fixed Dev mode

src/components/TitleBar.svelte

@@ -16,6 +16,10 @@
 
   const status = $derived(launcher.status);
   const checking = $derived(launcher.refreshing || status?.phase === "checking");
+  // The licence, not a setting: an operator's launcher must show no trace of dev mode.
+  const licensed = $derived((status?.dev ?? null) !== null);
+  const devOn = $derived(launcher.devOn);
+  const saving = $derived(launcher.busy === "settings");
 
   function windowAction(task: () => Promise<void>) {
     return () => {
@@ -80,6 +84,22 @@
 
   <div class="drag" data-tauri-drag-region></div>
 
+  {#if licensed}
+    <!-- Only on a PC that holds a dev licence. An operator's launcher never draws it, which
+         is the whole point of the licence - so this sits behind `status.dev`, not a setting. -->
+    <button
+      class="icon-btn dev"
+      class:on={devOn}
+      aria-label={devOn ? "Dev mode is on" : "Turn dev mode on"}
+      title={devOn ? "Dev mode is ON - ODIAN runs from your checkout" : "Dev mode"}
+      aria-pressed={devOn}
+      disabled={saving}
+      onclick={() => launcher.setDev({ dev_mode: !devOn })}
+    >
+      <Icon name="code" />
+    </button>
+  {/if}
+
   <button class="icon-btn market" aria-label="Marketplace" title="Marketplace" aria-haspopup="dialog" onclick={onOpenMarket}>
     <Icon name="market" />
   </button>
@@ -107,6 +127,18 @@
 </header>
 
 <style>
+  /* The dev switch. Off it is one more grey icon button; on it is unmistakably GREEN,
+     because "am I running my own build or the installed one" is the question this whole
+     mode exists to answer, and guessing it wrong wastes an afternoon. */
+  .icon-btn.dev.on {
+    color: #46d17f;
+    border-color: color-mix(in srgb, #46d17f 55%, transparent);
+    background: color-mix(in srgb, #46d17f 16%, transparent);
+  }
+  .icon-btn.dev.on:hover:not(:disabled) {
+    background: color-mix(in srgb, #46d17f 26%, transparent);
+  }
+
   .titlebar {
     position: relative;
     z-index: 20;