fix(vite): Skip HTML injection for MPA but keep it for SPA

[s1gr1d]

Fixes a regression introduced by PR #830 where debug IDs were not being injected into SPA main bundles. The original fix for issue #829 skipped all chunks with HTML facades to prevent creating unnecessary modules in Vite MPA builds. However, in SPAs, the main entry bundle also has an HTML facade but contains actual application code that needs debug ID injection.

This change adds a containsOnlyImports helper that checks whether a chunk's code is purely import/export statements. Now, HTML facade chunks are only skipped if they contain just imports (true MPA facades), while chunks with substantial code (SPA main bundles) get debug IDs injected as expected.

While the previous fix for #829 already added test cases, I also tested this locally with the reproduction example shared in the issue description. It still works as expected.

Closes #839

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

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Bug Fixes 🐛

Plugin Manager

• Respect sourcemap.ignore values for injecting debugIDs by s1gr1d in #836
• Enable "rejectOnError" in debug by s1gr1d in #837

Other

• (vite) Skip HTML injection for MPA but keep it for SPA by s1gr1d in #843

Documentation 📚

• Add RELEASE.md to document release process by nicohrubec in #834

Build / dependencies / internal 🔧

• (release) Switch from action-prepare-release to Craft by BYK in #831

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[logaretm]

Thanks for fixing this, good one!