Function record_missing_skill_content 

pub fn record_missing_skill_content(plan: &mut ExportPlan, missing: &[String])

Record that missing skill bundles contributed no content to the bundle.

The planner runs before any filesystem work, so it plans to carry every referenced bundle. Only the caller learns which of them actually had content, and the manifest is rendered from this plan: without folding that back in, a bundle would advertise skill_bundles and a carried_skills grant for a skills/<alias>/ tree it does not contain, and the only accurate record would be the terminal the export was run from.

Call before render_manifest_toml.