Phase 3 of SPEC-079. Removes the backwards-compat path in packages/transform/src/engine.ts that lets legacy slots: [...] + structure: {...} configs continue to render. Lands once all first-party plugins have migrated (WORK-306 through WORK-312 done) and the deprecation warning has been visible across at least one minor release.
Tracking started Jun 1 — check back for trends.
All first-party plugins migrated. Verify no plugin config declares the legacy slots: [...] array — git grep "slots: \[" in plugins/ and packages/runes/src/config.ts returns no matches.
Legacy shim code removed from packages/transform/src/engine.ts. Delete the else if (config.slots && config.structure) branch in transformRune, the hasLegacySlotNames helper, the warnLegacySlots helper, the LEGACY_SLOT_WARNED set, and the LEGACY_SLOT_NAMES constant.
Engine's structural-assembly path simplified. The legacy before/after assembly (else if (config.structure) branch) stays — it's used by non-meta-projecting runes that just inject icons or badges. Only the slot-based assembly tied to the legacy slot-name vocabulary is removed.
RuneConfig.slots field removed from types. With no remaining consumers, the type-level field comes out of packages/transform/src/types.ts. Comment updates in adjacent fields removed.
Universal .rf-badge class on legacy meta-typed structure entries removed. The shim path that added class="rf-badge" to every meta-typed StructureEntry (added in WORK-305) is no longer needed — runes that emit meta-typed structure entries directly are responsible for picking their own class. Most won't need it because all meta-projection went through metaFields.
Tests. Engine tests touching the legacy shim path (packages/transform/test/slots.test.ts etc.) updated or removed. CSS coverage tests in Lumina pass against the simplified surface.
Changeset. Marked as a minor version bump — the API change (removing RuneConfig.slots) is breaking for any third-party plugin that hasn't migrated. Changeset notes call this out and link to the SPEC-079 migration guide.
Docs. Theme-authoring docs that still describe the legacy slots + structure pattern updated. The dimensions.md "legacy StructureEntry fields" subsection trimmed or removed.
Pure cleanup work — wait until all first-party plugins are on the new path (WORK-307 through WORK-312 done), let one minor release ship with the deprecation warning visible to third-party plugin authors, then strip the shim.
The strip itself is mechanical: delete the slot-based assembly branch + helpers, drop RuneConfig.slots from the types, delete the legacy data-section / class="rf-badge" injections that exist only for the shim path.
Version bump: minor (breaking for any third-party plugin still on the legacy path; first-party plugins all migrated).