feat: prompt SpaceJoin when opening unjoined space via direct link

src/routes/spaces/[relay]/+layout.svelte

@@ -1,15 +1,21 @@
+<script module lang="ts">
+  const joinPrompted = new Set<string>()
+</script>
+
 <script lang="ts">
   import type {Snippet} from "svelte"
   import {page} from "$app/stores"
   import {once} from "@welshman/lib"
+  import {pubkey} from "@welshman/app"
   import Page from "@lib/components/Page.svelte"
   import SecondaryNav from "@lib/components/SecondaryNav.svelte"
   import SpaceMenu from "@app/components/SpaceMenu.svelte"
   import SpaceAuthError from "@app/components/SpaceAuthError.svelte"
   import SpaceTrustRelay from "@app/components/SpaceTrustRelay.svelte"
+  import SpaceJoin from "@app/components/SpaceJoin.svelte"
   import {pushModal} from "@app/util/modal"
   import {makeSpacePath} from "@app/util/routes"
-  import {decodeRelay, relaysPendingTrust} from "@app/core/state"
+  import {decodeRelay, userGroupList, relaysPendingTrust, userSpaceUrls} from "@app/core/state"
   import {deriveRelayAuthError} from "@app/core/commands"
 
   type Props = {
@@ -36,6 +42,27 @@
       showPendingTrust()
     }
   })
+
+  // Direct links skip Discover — prompt to join when relay is not in the user's space list.
+  const shouldPromptJoin = $derived.by(() => {
+    void $userGroupList
+
+    return (
+      Boolean($pubkey) &&
+      !$userSpaceUrls.includes(url) &&
+      !$authError &&
+      !$relaysPendingTrust.includes(url)
+    )
+  })
+
+  $effect(() => {
+    if (!shouldPromptJoin || joinPrompted.has(url)) {
+      return
+    }
+
+    joinPrompted.add(url)
+    pushModal(SpaceJoin, {url})
+  })
 </script>
 
 {#if $page.url.pathname === makeSpacePath(url)}