fix(installer): pass -IncludeDesktop to manifest, surface launch errors, alias hermes desktop

Three bugs found in the first VM end-to-end test:

1. install.ps1 -Manifest was called WITHOUT -IncludeDesktop, so the
   manifest came back with the 14-stage list (no desktop stage), the
   UI showed '14 steps' and Stage-Desktop never ran. Pass the flag to
   both the manifest fetch and the per-stage runs — install.ps1 gates
   the desktop stage's inclusion on the flag.

2. The Success screen's Launch button silently swallowed the Tauri
   error when no Hermes.exe existed (e.g. Stage-Desktop was skipped).
   Wire the error through to inline UI with an alert callout, so the
   user gets actionable text ('Hermes.exe missing, run hermes desktop
   from a terminal') instead of an unresponsive button.

3. The Success screen tells users to run 'hermes desktop' from a
   terminal but the CLI only accepted 'hermes gui' — invalid choice
   for 'desktop'. Rename the subcommand canonically to 'desktop' with
   'gui' as a backwards-compatible alias. Update the _SUBCOMMANDS sets
   used by session-flag arg parsing + logging-mode probe so both names
   route to the same logic.

apps/bootstrap-installer/src/routes/success.tsx

@@ -1,16 +1,37 @@
+import { useState } from 'react'
 import { type CSSProperties } from 'react'
 import { Button } from '../components/button'
 import { launchHermesDesktop } from '../store'
-import { Rocket } from 'lucide-react'
+import { Rocket, AlertCircle } from 'lucide-react'
 
 /*
  * Success screen. HERMES AGENT wordmark stays as the visual anchor
  * (same Collapse Bold treatment as Welcome + the desktop chat intro),
  * with a status line below.
  *
- * No install-path footer — same rationale as Welcome.
+ * Launching the desktop can fail (e.g. Stage-Desktop was skipped and
+ * Hermes.exe doesn't exist). We catch the Tauri error and surface it
+ * inline rather than silently doing nothing — the previous version
+ * had `onClick={() => void launchHermesDesktop()}` which swallowed
+ * the rejection and left the user staring at an unresponsive button.
  */
 export default function Success() {
+  const [error, setError] = useState<string | null>(null)
+  const [launching, setLaunching] = useState(false)
+
+  async function handleLaunch() {
+    setError(null)
+    setLaunching(true)
+    try {
+      await launchHermesDesktop()
+      // On success the installer exits — control never returns here.
+    } catch (e) {
+      const msg = e instanceof Error ? e.message : String(e)
+      setError(msg)
+      setLaunching(false)
+    }
+  }
+
   return (
     <div className="hermes-fade-in flex h-full flex-col items-center justify-center gap-8 px-12 py-10">
       <div className="w-full max-w-2xl min-w-0 text-center">
@@ -40,13 +61,27 @@ export default function Success() {
       </div>
 
       <Button
-        onClick={() => void launchHermesDesktop()}
+        onClick={() => void handleLaunch()}
         size="lg"
+        disabled={launching}
         className="inline-flex items-center gap-2 px-6"
       >
         <Rocket size={18} />
-        Launch Hermes
+        {launching ? 'Launching…' : 'Launch Hermes'}
       </Button>
+
+      {error && (
+        <div
+          role="alert"
+          className="flex max-w-2xl items-start gap-2 rounded-md border border-destructive/30 bg-destructive/10 px-4 py-3 text-sm text-destructive"
+        >
+          <AlertCircle size={16} className="mt-0.5 shrink-0" />
+          <div className="min-w-0">
+            <div className="font-medium">Couldn&rsquo;t launch the desktop app</div>
+            <div className="mt-1 text-destructive/80">{error}</div>
+          </div>
+        </div>
+      )}
     </div>
   )
 }