fix(channels): discord review round 5 — asset, channel fallback, media test

- Add a placeholder discord.png so the brand mark isn't a broken image
  (operators can swap in the official logo).
- Keep a saved Discord channel selectable before the live channel list loads
  (or if the lookup is unavailable), so editing a post never loses the channel.
- Cover the media multipart upload path (payload_json + files[N]) with a test.

resources/js/components/posts/editor/DiscordSettings.vue

@@ -87,6 +87,16 @@ const channelId = computed({
     set: (value: string) => updateMeta({ channel_id: value || null }),
 });
 
+// Keep a saved channel selectable even before the live list loads (or if the
+// lookup is unavailable), so editing a post never visually "loses" its channel.
+const channelOptions = computed<DiscordChannel[]>(() => {
+    if (channelId.value && !channels.value.some((channel) => channel.id === channelId.value)) {
+        return [{ id: channelId.value, name: channelId.value }, ...channels.value];
+    }
+
+    return channels.value;
+});
+
 const errors = usePageErrors();
 const channelError = computed<string | undefined>(() => {
     if (props.meta?.channel_id) {
@@ -202,7 +212,7 @@ const updateEmbed = (index: number, patch: Partial<EmbedDraft>) =>
                     <option value="">
                         {{ channelsLoading ? $t('posts.form.discord.loading_channels') : $t('posts.form.discord.select_channel') }}
                     </option>
-                    <option v-for="channel in channels" :key="channel.id" :value="channel.id">#{{ channel.name }}</option>
+                    <option v-for="channel in channelOptions" :key="channel.id" :value="channel.id">#{{ channel.name }}</option>
                 </select>
                 <InputError :message="channelError" />
             </div>

tests/Feature/Services/Social/DiscordPublisherTest.php

@@ -11,6 +11,7 @@
 use App\Models\SocialAccount;
 use App\Models\User;
 use App\Models\Workspace;
+use App\Services\Media\MediaOptimizer;
 use App\Services\Social\Discord\DiscordPublisher;
 use Illuminate\Support\Facades\Http;
 
@@ -120,6 +121,41 @@ function fakeDiscord(array $messageResponse = ['id' => '777'], int $status = 200
     });
 });
 
+test('uploads media as a multipart attachment', function () {
+    $this->post->update([
+        'media' => [[
+            'id' => 'm1',
+            'path' => 'media/2026-01/pic.jpg',
+            'url' => 'https://example.com/media/2026-01/pic.jpg',
+            'mime_type' => 'image/jpeg',
+            'original_filename' => 'pic.jpg',
+        ]],
+    ]);
+
+    $this->mock(MediaOptimizer::class)
+        ->shouldReceive('optimizeImage')
+        ->andReturnUsing(fn () => tap(tempnam(sys_get_temp_dir(), 'discord_test_'), fn ($f) => file_put_contents($f, str_repeat('x', 1024))));
+
+    Http::fake([
+        config('trypost.platforms.discord.api').'/guilds/*/channels' => Http::response([['id' => '444555666', 'name' => 'general', 'type' => 0]], 200),
+        'example.com/*' => Http::response(str_repeat('x', 1024), 200),
+        config('trypost.platforms.discord.api').'/channels/*/messages' => Http::response(['id' => '901'], 200),
+    ]);
+
+    $result = $this->publisher->publish(($this->makePostPlatform)());
+
+    expect($result['id'])->toBe('901');
+
+    Http::assertSent(function ($request) {
+        if (! str_contains($request->url(), '/messages')) {
+            return false;
+        }
+        $names = collect($request->data())->pluck('name');
+
+        return $names->contains('payload_json') && $names->contains('files[0]');
+    });
+});
+
 test('throws when no channel is selected', function () {
     expect(fn () => $this->publisher->publish(($this->makePostPlatform)(meta: [])))
         ->toThrow(DiscordPublishException::class);