refactor: flatten monorepo to single web package (#12)

Flatten the pnpm monorepo (apps/web + packages/*) into a single web package at the repo root.

- Move app/lib/components/scripts/public to root; drop apps/web and packages/* wrappers
- Rewrite tsconfig paths (@infiplot/*) to ./lib/*; turbopack.root = __dirname
- Update Vercel (no root-directory) and Cloudflare (pnpm build:cf at root) deploy paths
- Regenerate pnpm-lock.yaml to drop stale workspace importers
- Bump engines.node to >=22 to match wrangler

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/engine/vision.ts

@@ -0,0 +1,39 @@
+import { interpretClick } from "@infiplot/ai-client";
+import type {
+  ClickIntent,
+  ProviderConfig,
+  Scene,
+  VisionClassify,
+} from "@infiplot/types";
+import { parseJsonLoose } from "./jsonParser";
+import { VISION_SYSTEM_PROMPT, buildVisionUserPrompt } from "./prompts";
+
+export type VisionInterpretation = {
+  intent: ClickIntent;
+  classify: VisionClassify;
+};
+
+export async function interpret(
+  config: ProviderConfig,
+  annotatedImageBase64: string,
+  scene: Scene | null,
+): Promise<VisionInterpretation> {
+  const userPrompt = `${VISION_SYSTEM_PROMPT}\n\n${buildVisionUserPrompt(scene)}`;
+  const raw = await interpretClick(config, annotatedImageBase64, userPrompt);
+  const parsed = parseJsonLoose<{
+    freeformAction?: string;
+    classify?: string;
+    reasoning?: string;
+  }>(raw);
+
+  const classify: VisionClassify =
+    parsed.classify === "change-scene" ? "change-scene" : "insert-beat";
+
+  return {
+    intent: {
+      freeformAction: parsed.freeformAction?.trim() || "玩家点了画面，但意图不明",
+      reasoning: parsed.reasoning?.trim() || "",
+    },
+    classify,
+  };
+}