Fix Spicetify wrapper repair in Spotify setup

[yukazakiri]

Summary

Fixes /setup-spotify for source-built Spicetify packages that omit the generated spicetifyWrapper.js asset introduced in Spicetify v2.44.

Upstream context

This works around the upstream Spicetify packaging/build issue documented in spicetify/cli#3888.

Spicetify maintainers explain that since v2.44.0, the wrapper was made modular and spicetifyWrapper.js is no longer checked into the repository. It is generated from src/jsHelper/spicetifyWrapper during release builds by scripts/build-wrapper.mjs. Linux packages that build Spicetify from source without running that build step can install a CLI that still injects helper/spicetifyWrapper.js into Spotify, but does not ship the file. Their recommended manual fix is to install Node/pnpm, run pnpm build:wrapper, then run spicetify apply.

Details

This PR makes the Spotify setup recipe self-heal that state by:

• detecting a missing /opt/spicetify-cli/jsHelper/spicetifyWrapper.js
• reusing cached paru/yay Spicetify source when available
• downloading the matching release source when needed
• building the wrapper with pnpm, falling back to npm
• installing the generated wrapper into the package asset directory
• verifying the patched Spotify XPUI helper directory has the wrapper after spicetify backup apply

It also updates the Spicetify theme reapply script to preserve an already-built wrapper across future theme reapplies, and documents the setup behavior for maintainers.

Testing

• shellcheck scripts/setup/spotify.sh scripts/colors/apply-spicetify-theme.sh
• bash -n scripts/setup/spotify.sh scripts/colors/apply-spicetify-theme.sh
• bash scripts/setup/_scan.sh | jq -e '.[] | select(.slug=="spotify")'
• git diff --check