White screen for some users after a release: ChunkLoadError

• `Uncaught ChunkLoadError: Loading chunk 12 failed. (missing: https://cdn.example.cn/gis/js/12.8a4f1c2e.js)` at `__webpack_require__.e (bootstrap:64)`
• `curl -I https://cdn.example.cn/gis/index.html` returns `Cache-Control: public, max-age=86400`
• Repeated refreshes sometimes succeed, and different CDN nodes return different `ETag` values for the same HTML

1. Inspect the `Cache-Control` response header on `index.html`
2. Compare the chunk filename referenced by the CDN HTML with the files present on the origin
3. Request the same HTML through different regional nodes and compare `ETag` and body
4. Check whether the release process deletes the previous version's `js/` directory
5. Reproduce by loading a stale `index.html` from disk cache

Serve `index.html` with `Cache-Control: no-store, no-cache, must-revalidate` and keep hashed assets at `public, max-age=31536000, immutable`; retain one or two previous release directories and reload once on `ChunkLoadError`, guarded by a `sessionStorage` flag.

Uncaught ChunkLoadError: Loading chunk 12 failed.
(missing: https://cdn.example.cn/gis/js/12.8a4f1c2e.js)
    at __webpack_require__.e (bootstrap:64)

curl -I https://cdn.example.cn/gis/index.html
# Cache-Control: public, max-age=86400   ← HTML 被缓存一天，问题根源

curl -s https://cdn.example.cn/gis/index.html | grep -o 'js/[0-9a-f]*\.js'

• Giving `index.html` a long `max-age` for performance, which guarantees old HTML can reference deleted chunks
• Purging the CDN on release but not the browsers: already-cached HTML keeps requesting the removed chunk