fix: support legacy bundle checkouts

[huhuanming]

Summary

• keep the release bundle workflows compatible with legacy PR checkouts that predate the Rspack production-asset helper scripts
• skip web-embed Sentry debug-ID injection when the post-injection Chromium 67 checker is unavailable
• fall back to inline sourcemap and license-file cleanup for legacy web-embed and desktop bundles

Root cause

release-app-bundles runs the workflow definition from x but checks out the selected PR head before building. Release-branch PRs created before the Rspack migration do not contain check-browser-compat.js or finalize-production-assets.js, so the newer workflow failed with MODULE_NOT_FOUND after successful bundle compilation.

Impact

Legacy release PRs can be built by the current x workflow without shipping sourcemaps or license artifacts. Current checkouts retain the existing Sentry injection, Chromium 67 verification, and finalizer behavior.

Validation

• yarn lint:agent-context
• yarn lint:staged
• yarn tsc:staged
• YAML parse and Bash syntax checks for the modified workflow steps
• synthetic legacy production-asset cleanup check
• release-app-bundles run 29568580576: all web-embed, desktop, web, iOS, Android, and QA upload jobs passed