refactor(posts): tighten content-length caps and simplify contentOverflow

- Platform::contentOverflow returns int (0 = fits) via max(), drops the
  nullable-int + ternary pattern; HasSocialHttpClient and the validation
  rule updated to compare against 0 instead of null.
- Drop the hardcoded 63206-char limit to 10000 across all entry points
  (Platform enum, MCP CreatePostTool/UpdatePostTool, FacebookRules, all
  three FormRequests). Facebook's API accepts up to 63206 but nobody
  writes 63k-char posts and emoji-heavy content risks overflowing the
  TEXT column's 65535-byte ceiling.
- Compiled i18n JSON regenerated with the content_exceeds_platform key.

app/Ai/PlatformRules/FacebookRules.php

@@ -16,7 +16,7 @@ public function platform(): Platform
     public function specs(): array
     {
         return [
-            'max_content_length' => 63206,
+            'max_content_length' => 10000,
             'max_images' => 10,
             'text_only_allowed' => true,
             'formats' => [
@@ -30,7 +30,7 @@ public function specs(): array
     public function summary(): string
     {
         return <<<'TXT'
-Facebook: caption up to 63k chars but short posts perform better. Text-only allowed.
+Facebook: caption up to 10k chars but short posts perform better. Text-only allowed.
 - Post: flexible aspect ratio, up to 10 images/videos.
 - Reel: vertical 9:16 video only, up to 90s.
 - Story: vertical 9:16, single image/video, ephemeral.

app/Enums/SocialAccount/Platform.php

@@ -99,7 +99,9 @@ public function maxImages(): int
      *    (publisher derives title from the first line via `buildTitle`), and
      *    Shorts UX only shows ~100 chars before "more" — capping at 100 keeps
      *    posts appropriate for the format.
-     *  - Facebook text status: 63206
+     *  - Facebook text status: 10000 (API allows 63206; we cap below
+     *    that — 63k-char posts are unrealistic and emoji-heavy content
+     *    risks overflowing the TEXT column's 65535-byte ceiling)
      *  - Instagram feed caption: 2200
      *  - Threads: 500
      *  - Pinterest pin description: 800 (title is 100, not modeled here)
@@ -113,7 +115,7 @@ public function maxContentLength(): int
             self::X => 280,
             self::TikTok => 2200,
             self::YouTube => 100,
-            self::Facebook => 63206,
+            self::Facebook => 10000,
             self::Instagram, self::InstagramFacebook => 2200,
             self::Threads => 500,
             self::Pinterest => 800,
@@ -123,16 +125,14 @@ public function maxContentLength(): int
     }
 
     /**
-     * Number of characters the given content exceeds this platform's hard cap,
-     * or null when it fits. Single source of truth for content-length checks —
-     * used both at schedule/publish-validation time and at publish time itself
-     * so the two paths can never drift apart.
+     * Number of characters by which the given content exceeds this platform's
+     * hard cap. Returns 0 when it fits. Single source of truth for content-
+     * length checks — used both at schedule-validation time and at publish
+     * time itself so the two paths can never drift apart.
      */
-    public function contentOverflow(string $content): ?int
+    public function contentOverflow(string $content): int
     {
-        $over = mb_strlen($content) - $this->maxContentLength();
-
-        return $over > 0 ? $over : null;
+        return max(0, mb_strlen($content) - $this->maxContentLength());
     }
 
     /**

app/Http/Requests/Api/Post/StorePostRequest.php

@@ -28,7 +28,7 @@ public function rules(): array
             'content' => [
                 'nullable',
                 'string',
-                'max:63206',
+                'max:10000',
                 Rule::when(
                     $this->filled('scheduled_at'),
                     [new ContentFitsPlatformLimits($this->resolveSelectedPlatforms($workspaceId))]

app/Http/Requests/Api/Post/UpdatePostRequest.php

@@ -35,7 +35,7 @@ public function rules(): array
             'content' => [
                 'nullable',
                 'string',
-                'max:63206',
+                'max:10000',
                 Rule::when(
                     $enforcesPlatformLimits,
                     [new ContentFitsPlatformLimits($this->resolveSelectedPlatforms())]

app/Http/Requests/App/Post/UpdatePostRequest.php

@@ -34,7 +34,7 @@ public function rules(): array
             'content' => [
                 'nullable',
                 'string',
-                'max:63206',
+                'max:10000',
                 Rule::when(
                     $enforcesMediaCompatibility,
                     [new ContentFitsPlatformLimits($this->resolveSelectedPlatforms())]

app/Mcp/Tools/Post/CreatePostTool.php

@@ -24,7 +24,7 @@ public function handle(Request $request): ResponseFactory
         $workspace = $request->user()->currentWorkspace;
 
         $validated = $request->validate([
-            'content' => ['nullable', 'string', 'max:63206'],
+            'content' => ['nullable', 'string', 'max:10000'],
             'scheduled_at' => ['nullable', 'date', 'after:now'],
             'label_ids' => ['sometimes', 'array'],
             'label_ids.*' => ['uuid', Rule::exists('workspace_labels', 'id')->where('workspace_id', $workspace->id)],

app/Mcp/Tools/Post/UpdatePostTool.php

@@ -35,7 +35,7 @@ public function handle(Request $request): Response|ResponseFactory
 
         $validated = $request->validate([
             'post_id' => ['required', 'uuid'],
-            'content' => ['nullable', 'string', 'max:63206'],
+            'content' => ['nullable', 'string', 'max:10000'],
             'scheduled_at' => ['nullable', 'date', 'after:now'],
             'status' => ['sometimes', 'string', Rule::in([Status::Draft->value, Status::Scheduled->value])],
             'label_ids' => ['sometimes', 'array'],

app/Rules/ContentFitsPlatformLimits.php

@@ -41,7 +41,7 @@ public function validate(string $attribute, mixed $value, Closure $fail): void
             }
 
             $over = $platform->contentOverflow($content);
-            if ($over === null) {
+            if ($over === 0) {
                 continue;
             }
 

app/Services/Social/Concerns/HasSocialHttpClient.php

@@ -16,7 +16,7 @@ protected function validateContentLength(PostPlatform $postPlatform): void
     {
         $content = $postPlatform->post->content ?? '';
 
-        if ($postPlatform->platform->contentOverflow($content) === null) {
+        if ($postPlatform->platform->contentOverflow($content) === 0) {
             return;
         }
 

tests/Unit/Enums/PlatformTest.php

@@ -60,7 +60,7 @@
     expect(Platform::X->maxContentLength())->toBe(280);
     expect(Platform::TikTok->maxContentLength())->toBe(2200);
     expect(Platform::YouTube->maxContentLength())->toBe(100);
-    expect(Platform::Facebook->maxContentLength())->toBe(63206);
+    expect(Platform::Facebook->maxContentLength())->toBe(10000);
     expect(Platform::Instagram->maxContentLength())->toBe(2200);
     expect(Platform::Threads->maxContentLength())->toBe(500);
     expect(Platform::Pinterest->maxContentLength())->toBe(800);