feat(turbopack): support script bootstraps with shared runtime

[fireairforce]

Summary

Consumers that load browser entry scripts directly cannot use the shared production runtime when entry bootstrap parameters are returned only for HTML inlining. Add an opt-in emit_entry_bootstrap builder option that keeps the existing bootstrap script alongside the shared runtime, retaining the runtime as the last chunk-group asset. The option defaults to false, preserving existing consumers.

Export EcmascriptBrowserRuntimeChunk so integrations can include the shared runtime when selecting initial script assets. This is the prerequisite for Utoo's separate shared-runtime configuration change.

Verification

• Built the changed Turbopack crates through Utoo's native addon with cargo build --locked --profile release-local -p pack-napi --features plugin.
• Real Chrome checks through Utoo passed for single and multiple entries, dynamic imports, Worker dynamic imports, root/non-root public paths, and generated HTML with blocking/deferred scripts.
• A real twenty-entry fixture passed in both modes. All entries referenced one shared runtime with no identical-content aliases. Total emitted JavaScript decreased by 210,919 raw bytes and 77,409 bytes of per-file gzip; a single entry's initial load did not become smaller.
• Turbopack browser formatting, Utoo workspace Clippy, and plugin-feature Clippy passed. Full Next.js integration suites were not run; validation exercised the Rust interface through its Utoo consumer.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-29T02:59:05.751893Z	c037804	Draft marked ready

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