feat(smart-crop): overhaul with face detection, social presets, and 3 modes

Replace the confusing 2-mode smart crop with a clear 3-mode system:
- Subject Focus: Sharp attention/entropy saliency crop with social media presets
- Face Focus: MediaPipe face detection with headshot framing presets
- Auto Trim: Border removal with optional pad-to-square

Adds detectFaces() to AI package, face preset constants, backward
compatibility for old mode names, and comprehensive integration tests.

packages/ai/python/detect_faces.py

@@ -15,6 +15,7 @@ def main():
 
     blur_radius = settings.get("blurRadius", 30)
     sensitivity = settings.get("sensitivity", 0.5)
+    detect_only = settings.get("detectOnly", False)
 
     try:
         emit_progress(10, "Preparing")
@@ -64,26 +65,30 @@ def main():
                     w = int(bbox.width * iw)
                     h = int(bbox.height * ih)
 
-                    # Add padding around the face
-                    pad = int(max(w, h) * 0.1)
-                    x1 = max(0, x - pad)
-                    y1 = max(0, y - pad)
-                    x2 = min(img.width, x + w + pad)
-                    y2 = min(img.height, y + h + pad)
+                    if not detect_only:
+                        # Add padding around the face
+                        pad = int(max(w, h) * 0.1)
+                        x1 = max(0, x - pad)
+                        y1 = max(0, y - pad)
+                        x2 = min(img.width, x + w + pad)
+                        y2 = min(img.height, y + h + pad)
+
+                        face_region = img.crop((x1, y1, x2, y2))
+                        blurred = face_region.filter(
+                            ImageFilter.GaussianBlur(blur_radius)
+                        )
+                        img.paste(blurred, (x1, y1))
+                        emit_progress(
+                            50 + int((i + 1) / num_faces * 40),
+                            f"Blurring face {i + 1} of {num_faces}",
+                        )
 
-                    face_region = img.crop((x1, y1, x2, y2))
-                    blurred = face_region.filter(
-                        ImageFilter.GaussianBlur(blur_radius)
-                    )
-                    img.paste(blurred, (x1, y1))
                     faces.append({"x": x, "y": y, "w": w, "h": h})
-                    emit_progress(
-                        50 + int((i + 1) / num_faces * 40),
-                        f"Blurring face {i + 1} of {num_faces}",
-                    )
 
-            emit_progress(95, "Saving result")
-            img.save(output_path)
+            if not detect_only:
+                emit_progress(95, "Saving result")
+                img.save(output_path)
+
             print(
                 json.dumps(
                     {

packages/ai/src/face-detection.ts

@@ -1,4 +1,5 @@
-import { readFile, writeFile } from "node:fs/promises";
+import { readFile, unlink, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { type ProgressCallback, runPythonWithProgress } from "./bridge.js";
 
@@ -7,6 +8,10 @@ export interface BlurFacesOptions {
   sensitivity?: number;
 }
 
+export interface DetectFacesOptions {
+  sensitivity?: number;
+}
+
 export interface FaceRegion {
   x: number;
   y: number;
@@ -20,6 +25,11 @@ export interface BlurFacesResult {
   faces: FaceRegion[];
 }
 
+export interface DetectFacesResult {
+  facesDetected: number;
+  faces: FaceRegion[];
+}
+
 export async function blurFaces(
   inputBuffer: Buffer,
   outputDir: string,
@@ -48,3 +58,32 @@ export async function blurFaces(
     faces: result.faces ?? [],
   };
 }
+
+export async function detectFaces(
+  inputBuffer: Buffer,
+  options: DetectFacesOptions = {},
+  onProgress?: ProgressCallback,
+): Promise<DetectFacesResult> {
+  const inputPath = join(tmpdir(), `detect_faces_${Date.now()}.png`);
+
+  try {
+    await writeFile(inputPath, inputBuffer);
+    const { stdout } = await runPythonWithProgress(
+      "detect_faces.py",
+      [inputPath, "unused", JSON.stringify({ ...options, detectOnly: true })],
+      { onProgress },
+    );
+
+    const result = JSON.parse(stdout);
+    if (!result.success) {
+      throw new Error(result.error || "Face detection failed");
+    }
+
+    return {
+      facesDetected: result.facesDetected,
+      faces: result.faces ?? [],
+    };
+  } finally {
+    await unlink(inputPath).catch(() => {});
+  }
+}

packages/ai/src/index.ts

@@ -1,6 +1,7 @@
 export { removeBackground } from "./background-removal.js";
 export { isGpuAvailable, shutdownDispatcher } from "./bridge.js";
-export { blurFaces } from "./face-detection.js";
+export type { DetectFacesResult, FaceRegion } from "./face-detection.js";
+export { blurFaces, detectFaces } from "./face-detection.js";
 export { inpaint } from "./inpainting.js";
 export { extractText } from "./ocr.js";
 export { seamCarve } from "./seam-carving.js";