feat: VITE_DEV_TOOLS env-gate for preview tooling on deployed builds

Adds a useDevTools() composable that returns true when either Vite's
own DEV flag is set (local pnpm dev) or VITE_DEV_TOOLS='true' is
passed at build time. AppLayout's PaletteSwitcher now reads through
this composable, so the picker can render on earthwalker.aiolabs.dev
without flipping the build to development mode.

Single gate intentionally — future preview-only surfaces (debug
overlays, unfinished pages, work-in-progress UI) hook into the same
composable. Anything Nicholette should see but the public shouldn't
becomes a v-if="devTools" check. Set the var on the deploy host,
rebuild, surfaces appear; unset, surfaces vanish.

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

.env.example

@@ -13,3 +13,9 @@ VITE_OWNER_NPUB=
 #   wss://relay.damus.io,wss://nos.lol,wss://relay.nostr.band
 # The submission succeeds if at least one relay accepts the event.
 VITE_NOSTR_RELAYS=
+
+# Optional. Set to "true" to expose in-progress preview tooling on a
+# production build — the palette picker today, future debug overlays
+# or unfinished pages tomorrow. Gated through useDevTools(); unset
+# (or anything other than "true") strips them.
+VITE_DEV_TOOLS=

env.d.ts

@@ -5,6 +5,10 @@ interface ImportMetaEnv {
   readonly VITE_OWNER_NPUB?: string
   /** Comma-separated wss:// relay list; falls back to a default set if unset. */
   readonly VITE_NOSTR_RELAYS?: string
+  /** When set to 'true', in-progress preview tooling (the palette
+   * picker today, future debug overlays / unfinished pages) renders
+   * in any build. Gated via useDevTools(). */
+  readonly VITE_DEV_TOOLS?: string
 }
 
 interface ImportMeta {

src/components/layout/AppLayout.vue

@@ -4,8 +4,9 @@ import { Toaster } from '@/components/ui/sonner'
 import SiteHeader from './SiteHeader.vue'
 import SiteFooter from './SiteFooter.vue'
 import PaletteSwitcher from './PaletteSwitcher.vue'
+import { useDevTools } from '@/composables/useDevTools'
 
-const isDev = import.meta.env.DEV
+const { enabled: devTools } = useDevTools()
 </script>
 
 <template>
@@ -16,6 +17,6 @@ const isDev = import.meta.env.DEV
     </main>
     <SiteFooter />
     <Toaster position="bottom-right" />
-    <PaletteSwitcher v-if="isDev" />
+    <PaletteSwitcher v-if="devTools" />
   </div>
 </template>

src/composables/useDevTools.ts

@@ -0,0 +1,14 @@
+/**
+ * True when the build should expose in-progress / preview tooling
+ * (the palette picker, future debug overlays, unfinished pages, etc.).
+ *
+ * Always true in local `pnpm dev` (Vite sets `import.meta.env.DEV`).
+ * Otherwise opted-in by setting `VITE_DEV_TOOLS=true` at build time —
+ * useful for a deployed preview the client uses to evaluate
+ * in-progress work.
+ */
+export function useDevTools() {
+  const enabled =
+    import.meta.env.DEV || import.meta.env.VITE_DEV_TOOLS === 'true'
+  return { enabled }
+}