Track Hinode/Hugo deprecation warnings, plan Dart Sass migration

[gjong]

Labels: maintenance, tech-debt, priority:P3
Parent issue: Epic: Documentation site overhaul

Problem
Build currently warns about .Site.Data, libsass, and module mounts. Hugo is expected to eventually drop libsass support.

Suggested fix

• Monitor Hinode releases for these deprecations.
• Plan and schedule migration to Dart Sass before it becomes a hard build break.

Acceptance criteria

• Build produces no deprecation warnings, or warnings are tracked with a target Hinode/Hugo version for resolution.