[rz1989s]

Compat run for omp v18.12.5 (span 18.12.4 → 18.12.5).

• Surface: UNCHANGED — no context/event/theme/widget/JSONL-schema changes; span's one breaking item (pi-utils tar Promise) is compile-time unreachable (zero @oh-my-pi/* imports). Additive ctx.ui.getEditorComponent() unused.
• Bonus: 18.12.4 #12653 fixes omp exiting when the model picker opens after compatibility extensions load.
• Gates: typecheck ✓, 62/62 tests ✓; formatter sim 6/6 exact groups; binary-window containment 79 lines, 0 contradictions.
• Docs: README feature-table row + hero.svg tspan → omp 18.12.5 · sl 0.8.7 · tern 0.7.2 (real versionLine output); COMPATIBILITY.md archive section appended.
• Version: 0.8.6 → 0.8.7 (docs-only patch).