chore: Bump version to 0.1.3

- Fix: Skip empty/whitespace-only text content blocks in chat completions
- This resolves Anthropic API errors:
  - "messages: text content blocks must contain non-whitespace text"
  - "messages: text content blocks must be non-empty"
- Updated version strings in all test files and snapshots

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

llmx-rs/core/src/chat_completions.rs

@@ -175,7 +175,10 @@ pub(crate) async fn stream_chat_completions(
                         ContentItem::InputText { text: t }
                         | ContentItem::OutputText { text: t } => {
                             text.push_str(t);
-                            items.push(json!({"type":"text","text": t}));
+                            // Only add text content blocks that are non-empty
+                            if !t.trim().is_empty() {
+                                items.push(json!({"type":"text","text": t}));
+                            }
                         }
                         ContentItem::InputImage { image_url } => {
                             saw_image = true;
@@ -184,6 +187,11 @@ pub(crate) async fn stream_chat_completions(
                     }
                 }
 
+                // Skip messages with empty or whitespace-only text content (unless they contain images)
+                if text.trim().is_empty() && !saw_image {
+                    continue;
+                }
+
                 // Skip exact-duplicate assistant messages.
                 if role == "assistant" {
                     if let Some(prev) = &last_assistant_text