feat: add @automaker/utils package

- Extract error handling utilities (isAbortError, classifyError, etc.)
- Extract conversation utilities (formatHistoryAsText, etc.)
- Extract image handling utilities (readImageAsBase64, etc.)
- Extract prompt building utilities (buildPromptWithImages)
- Extract logger utilities (createLogger, setLogLevel)
- Extract file system utilities (mkdirSafe, existsSafe)

All utilities now use @automaker/types for type imports.
Provides shared utility functions for both server and UI.

Dependencies: @automaker/types

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

libs/utils/src/prompt-builder.ts

@@ -0,0 +1,79 @@
+/**
+ * Prompt building utilities for constructing prompts with images
+ *
+ * Provides standardized prompt building that:
+ * - Combines text prompts with image attachments
+ * - Handles content block array generation
+ * - Optionally includes image paths in text
+ * - Supports both vision and non-vision models
+ */
+
+import { convertImagesToContentBlocks, formatImagePathsForPrompt } from "./image-handler";
+
+/**
+ * Content that can be either simple text or structured blocks
+ */
+export type PromptContent = string | Array<{
+  type: string;
+  text?: string;
+  source?: object;
+}>;
+
+/**
+ * Result of building a prompt with optional images
+ */
+export interface PromptWithImages {
+  content: PromptContent;
+  hasImages: boolean;
+}
+
+/**
+ * Build a prompt with optional image attachments
+ *
+ * @param basePrompt - The text prompt
+ * @param imagePaths - Optional array of image file paths
+ * @param workDir - Optional working directory for resolving relative paths
+ * @param includeImagePaths - Whether to append image paths to the text (default: false)
+ * @returns Promise resolving to prompt content and metadata
+ */
+export async function buildPromptWithImages(
+  basePrompt: string,
+  imagePaths?: string[],
+  workDir?: string,
+  includeImagePaths: boolean = false
+): Promise<PromptWithImages> {
+  // No images - return plain text
+  if (!imagePaths || imagePaths.length === 0) {
+    return { content: basePrompt, hasImages: false };
+  }
+
+  // Build text content with optional image path listing
+  let textContent = basePrompt;
+  if (includeImagePaths) {
+    textContent += formatImagePathsForPrompt(imagePaths);
+  }
+
+  // Build content blocks array
+  const contentBlocks: Array<{
+    type: string;
+    text?: string;
+    source?: object;
+  }> = [];
+
+  // Add text block if we have text
+  if (textContent.trim()) {
+    contentBlocks.push({ type: "text", text: textContent });
+  }
+
+  // Add image blocks
+  const imageBlocks = await convertImagesToContentBlocks(imagePaths, workDir);
+  contentBlocks.push(...imageBlocks);
+
+  // Return appropriate format
+  const content: PromptContent =
+    contentBlocks.length > 1 || contentBlocks[0]?.type === "image"
+      ? contentBlocks
+      : textContent;
+
+  return { content, hasImages: true };
+}