feat: omp 18.9.2 compatibility (docs/version update)

[rz1989s]

Compat run for omp v18.9.2 via /compat-update.

• Surface: UNCHANGED — release is host-internal (pi-ai judge renames, coding-agent/tui fixes, Tern-in-tmux TSP rendering); no extension-context, theme, session-JSONL, or plugin-loading change.
• Gates: typecheck ✓, tests 62/62 ✓
• Render sim: formatter-level ✓ (all six rows + degradation probes); live tmux verify post-publish
• Verdict: COMPATIBLE → docs-only patch 0.8.0 → 0.8.1
• Docs: README versions-row mock refreshed via real formatter; docs/COMPATIBILITY.md archive created

Archive: docs/COMPATIBILITY.md