update

src/components/SettingsDrawer.svelte

@@ -23,6 +23,9 @@
   const current = $derived(launcher.settings);
   const locked = $derived(launcher.locked);
   const saving = $derived(launcher.busy === "settings");
+  /** A launcher that ships on an ODIAN drive installs on that drive to run ODIAN from it,
+   * or on a disk of the PC it is plugged into to hand ODIAN over. */
+  const portable = $derived(s?.portable ?? false);
   const busy = $derived(launcher.busy !== null);
 
   const trimmed = $derived<Settings>({
@@ -36,10 +39,12 @@
         trimmed.mcp_url !== current.mcp_url ||
         trimmed.install_dir !== current.install_dir),
   );
+  /** A drive's launcher needs a folder on a disk: a root or a share holds no install. */
+  const offDrive = $derived(portable && trimmed.install_dir !== "" && !/^[A-Za-z]:\\.+/.test(trimmed.install_dir));
   const siteError = $derived(urlProblem(trimmed.site_url));
   const mcpError = $derived(urlProblem(trimmed.mcp_url));
   const dirError = $derived(trimmed.install_dir ? null : "Choose where ODIAN is installed.");
-  const invalid = $derived(siteError !== null || mcpError !== null || dirError !== null);
+  const invalid = $derived(siteError !== null || mcpError !== null || dirError !== null || offDrive);
 
   function urlProblem(value: string): string | null {
     if (!value) return "Required.";
@@ -134,7 +139,7 @@
 
   function installFromDrive() {
     open = false;
-    void launcher.installFromDrive();
+    void launcher.chooseDrive();
   }
 
   function signIn() {
@@ -216,14 +221,24 @@
             </button>
           </div>
           <span id="set-install-dir-help" class={dirty && dirError ? "field-error" : "field-help"}>
-            {dirty && dirError ? dirError : "Application, database snapshot and map tiles live here."}
+            {#if offDrive}
+              Give a folder on a disk, like D:\ODIAN — not a drive's root, and not a network share.
+            {:else if portable}
+              On the ODIAN drive this launcher runs from, ODIAN runs from the drive and follows it to the
+              next PC. A folder on this PC's own disk installs ODIAN onto the PC instead.
+            {:else}
+              {dirty && dirError ? dirError : "Application, database snapshot and map tiles live here."}
+            {/if}
           </span>
         </div>
       </fieldset>
 
       <section class="group" aria-labelledby="set-drive-title">
         <h3 id="set-drive-title" class="eyebrow">Install from drive</h3>
-        <p class="text">Install or update from an ODIAN SSD without reaching the DHP. Pick the drive's root folder.</p>
+        <p class="text">
+          Copy ODIAN from an ODIAN SSD into your install folder, without reaching the DHP. Pick the drive,
+          then choose what to copy.
+        </p>
         <div>
           <button type="button" class="btn" disabled={locked || busy} onclick={installFromDrive}>
             <Icon name="drive" size={14} /> Install from drive…