feat: replace Python seam carving with caire Go binary

Replace the Python seam-carving library with caire (esimov/caire v1.5.0),
a Go-based content-aware resize engine that is faster and supports both
shrinking and enlarging via seam insertion.

- Add Go builder stage in Dockerfile to compile caire from source
- Rewrite seam-carving.ts to call caire via execFile (no Python sidecar)
- Remove content-aware-resize from PYTHON_SIDECAR_TOOLS (60s timeout)
- Add new options: blur radius, edge sensitivity, square mode, face detection
- Move content-aware toggle below standard resize in UI (subtler placement)
- Rename "Don't enlarge" to "Limit to original size" with hover tooltip
- Add smooth progress bar for medium-duration tools
- Delete seam_carve.py and remove seam-carving pip dependency
- Update integration tests and visual regression screenshots

packages/ai/src/seam-carving.ts

@@ -1,11 +1,19 @@
-import { readFile, writeFile } from "node:fs/promises";
+import { execFile } from "node:child_process";
+import { randomUUID } from "node:crypto";
+import { readFile, rm, writeFile } from "node:fs/promises";
 import { join } from "node:path";
-import { type ProgressCallback, runPythonWithProgress } from "./bridge.js";
+import { promisify } from "node:util";
+import sharp from "sharp";
+
+const execFileAsync = promisify(execFile);
 
 export interface SeamCarveOptions {
   width?: number;
   height?: number;
   protectFaces?: boolean;
+  blurRadius?: number;
+  sobelThreshold?: number;
+  square?: boolean;
 }
 
 export interface SeamCarveResult {
@@ -14,31 +22,77 @@ export interface SeamCarveResult {
   height: number;
 }
 
+/**
+ * Discover the caire binary. Checks PATH (Docker installs to /usr/local/bin)
+ * and the CAIRE_PATH env var for local development.
+ */
+let cachedCairePath: string | null = null;
+
+async function findCaire(): Promise<string> {
+  if (cachedCairePath) return cachedCairePath;
+
+  const candidates = process.env.CAIRE_PATH ? [process.env.CAIRE_PATH, "caire"] : ["caire"];
+
+  for (const cmd of candidates) {
+    try {
+      await execFileAsync(cmd, ["-help"], { timeout: 5_000 });
+      cachedCairePath = cmd;
+      return cmd;
+    } catch {
+      // try next
+    }
+  }
+  throw new Error(
+    "caire binary not found. Install via: go install github.com/esimov/caire/cmd/caire@v1.5.0",
+  );
+}
+
+/**
+ * Content-aware resize using caire (Go seam carving engine).
+ * Supports both shrinking and enlarging via seam removal/insertion.
+ */
 export async function seamCarve(
   inputBuffer: Buffer,
   outputDir: string,
   options: SeamCarveOptions = {},
-  onProgress?: ProgressCallback,
 ): Promise<SeamCarveResult> {
-  const inputPath = join(outputDir, "input_seam_carve.png");
-  const outputPath = join(outputDir, "output_seam_carve.png");
+  const cairePath = await findCaire();
+  const id = randomUUID();
+  const inputPath = join(outputDir, `caire-in-${id}.png`);
+  const outputPath = join(outputDir, `caire-out-${id}.png`);
 
-  await writeFile(inputPath, inputBuffer);
-  const { stdout } = await runPythonWithProgress(
-    "seam_carve.py",
-    [inputPath, outputPath, JSON.stringify(options)],
-    { onProgress },
-  );
+  try {
+    await writeFile(inputPath, inputBuffer);
 
-  const result = JSON.parse(stdout);
-  if (!result.success) {
-    throw new Error(result.error || "Content-aware resize failed");
+    // Build caire arguments
+    const args = ["-in", inputPath, "-out", outputPath, "-preview=false"];
+
+    if (options.square) {
+      // Caire -square requires -width and -height set to the shortest edge
+      const meta = await sharp(inputBuffer).metadata();
+      const shortest = Math.min(meta.width ?? 0, meta.height ?? 0);
+      args.push("-square", "-width", String(shortest), "-height", String(shortest));
+    } else {
+      if (options.width) args.push("-width", String(options.width));
+      if (options.height) args.push("-height", String(options.height));
+    }
+
+    if (options.protectFaces) args.push("-face");
+    if (options.blurRadius !== undefined) args.push("-blur", String(options.blurRadius));
+    if (options.sobelThreshold !== undefined) args.push("-sobel", String(options.sobelThreshold));
+
+    await execFileAsync(cairePath, args, { timeout: 60_000 });
+
+    const buffer = await readFile(outputPath);
+    const meta = await sharp(buffer).metadata();
+
+    return {
+      buffer,
+      width: meta.width ?? 0,
+      height: meta.height ?? 0,
+    };
+  } finally {
+    await rm(inputPath, { force: true }).catch(() => {});
+    await rm(outputPath, { force: true }).catch(() => {});
   }
-
-  const buffer = await readFile(outputPath);
-  return {
-    buffer,
-    width: result.width,
-    height: result.height,
-  };
 }