perf: faster plugin updates, half-size first bundle, images from the chat attach on Windows

- Chat view: an attached image's path is pasted on its own after the text
  (promptForPane). claude turns a paste that is only an image path into
  [Image #n], but left a Windows path inside a paste of text as a plain path.
  Other files and @-mentions stay in the text as before.
- Plugin bootstrap: depsHash covers only what npm installs (no release
  version), so a version bump no longer reinstalls runtime deps; the client's
  installed tree is kept while its manifests are unchanged (no npm ci per
  update); the user-side build runs vite only (tsc -b cost ~25 s / ~900 MB);
  clientBuild is recorded only after a build that did not fail, so a failed
  one is retried; npm output goes to runtime/npm-install.log.
- Server: a port held by another program ends with a clear message and exit 1
  instead of an uncaught 'error' stack trace.
- Client: the onboarding wizard is lazy and rendered only before onboarding;
  usePrefersReducedMotion moved to hooks/ so PetSettings no longer pulls the
  Sagi chat/pane stack into the entry chunk (884 KB -> 431 KB, gzip 268 -> 133 KB).

client/src/hooks/usePrefersReducedMotion.ts

@@ -0,0 +1,27 @@
+/**
+ * @file usePrefersReducedMotion.ts
+ * @description The OS "reduce motion" preference, followed live. Its own
+ * module so a settings screen can read it without importing the pet overlay
+ * (`components/Sagi/Sagi.tsx`), whose chat and pane UI would otherwise be
+ * pulled into every page's first bundle.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { useEffect, useState } from "react";
+
+/** The OS "reduce motion" preference, followed live. */
+export function usePrefersReducedMotion(): boolean {
+  const [reduced, setReduced] = useState(
+    () =>
+      typeof window !== "undefined" &&
+      window.matchMedia?.("(prefers-reduced-motion: reduce)").matches
+  );
+  useEffect(() => {
+    const mq = window.matchMedia?.("(prefers-reduced-motion: reduce)");
+    if (!mq) return;
+    const onChange = () => setReduced(mq.matches);
+    mq.addEventListener?.("change", onChange);
+    return () => mq.removeEventListener?.("change", onChange);
+  }, []);
+  return reduced;
+}