Retire Legacy Runtime Directory Helpers

[jeremymcs]

What to build

Retire or narrow legacy runtime directory helper surfaces after runtime metadata is shared through the runtime registry projection. Callers should consume explicit policy projections instead of one-off helper functions that can drift from install/runtime query behavior.

Acceptance criteria

• Obsolete one-off runtime directory helpers are removed or made private behind the runtime policy projection.
• Remaining helper exports are justified by current external tests or compatibility needs.
• OpenCode and Kilo directory precedence behavior remains covered after helper cleanup.
• Full installer and runtime-global skills tests pass.

Blocked by

• Deduplicate Runtime Metadata Across Install and SDK Query Surfaces #3371

[github-actions]

Branch chore/3374-retire-legacy-runtime-directory-helpers created.

git fetch origin && git checkout chore/3374-retire-legacy-runtime-directory-helpers

[github-actions]

Branch feat/3374-retire-legacy-runtime-directory-helpers created.

git fetch origin && git checkout feat/3374-retire-legacy-runtime-directory-helpers