feat: omp 18.11.0 compatibility

[rz1989s]

Compat run for omp v18.11.0. Span cleared: 18.10.2, 18.10.3, 18.10.4, 18.11.0 (GitHub release bodies + embedded binary changelog, sources agree).

• Surface UNCHANGED: no ctx/event/theme/JSONL-schema change on the plugin's surface. All breaking removals in the span live in packages/members the plugin never imports (zero @oh-my-pi/* deps). 18.11.0 #15680 build-stamp fields are additive; money.ts typeof-guards ignore them.
• Gates: typecheck clean, 62/62 tests.
• Formatter sim: exact-equality renders incl. target probe versionLine({omp:"18.11.0", sl:"0.8.4"}).
• Docs: README feature-table row + hero.svg versions tspan → omp 18.11.0 · sl 0.8.4; COMPATIBILITY.md archive section.
• Version: 0.8.3 → 0.8.4 (docs-only patch).