Upgrade @embroider/addon-dev to unblock gts

[shleewhite]

📌 Summary

If merged, this PR would unblock the rest of the gts conversions because it upgrades @embroider/addon-dev to v8 which has a fix for the whitespace issues.

Changes include also include: pull in the new rollup config from Project Solar which fixes how the sass/css files are compiled for the dist (#3237). This is because in @embroider/addon-dev v8, it stops automatically copying over all the assets to the dist unless done explicitly and the config in Project Solar fixes this.

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📋 PCI review checklist

• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.
• If applicable, I've worked with GRC to document the impact of any changes to security controls.
  Examples of changes to controls include access controls, encryption, logging, etc.
• If applicable, I've worked with GRC to ensure compliance due to a significant change to the in-scope PCI environment.
  Examples include changes to operating systems, ports, protocols, services, cryptography-related components, PII processing code, etc.

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Project	Deployment	Review	Updated (UTC)
hds-showcase	Ready	Preview	Jan 28, 2026 2:13pm
hds-website	Ready	Preview	Jan 28, 2026 2:13pm

[didoo]

Nice! 👍