core runs its suite via `vitest run` (include: src/**/*.test.ts), so the bun:test
import broke vitest collection ("Module bun:test has been externalized"), turning
core CI red on main and on every open PR (which build against the merge ref).
vitest's describe/it/expect are API-compatible — no test changes needed.
Extract cssAttrSelector to packages/core/src/utils/cssSelector.ts and
use it (or CSS.escape for browser-side code) at all 12 sites that
previously interpolated raw user-authored values into querySelector
attribute selectors. A " in a composition ID, script src, or
data-start value would produce a malformed selector that throws.
Node-side (core compiler/parser): uses the shared cssAttrSelector.
Browser-side (runtime, studio): uses native CSS.escape().
Supersedes #1568 which fixed only the 3 bundler sites.
Miguel Ángel