docs: drop dangling FOCAS refs + link unreferenced v2 design docs

- docs/drivers/FOCAS.md and docs/v2/implementation/focas-wire-protocol.md
  pointed at focas-deployment.md and focas-simulator-plan.md, both of
  which were untracked drafts that have since been removed. Drop the
  refs (the wire-protocol companion now stands on its own; deployment
  guidance lives inline in the FOCAS driver doc).
- Link the orphan v2 design docs from docs/README.md (multi-host
  dispatch, v2 release readiness, the historical lmx-followups tracker)
  and from modbus-test-plan.md (s7.md, mitsubishi.md per-family quirk
  catalogs, sibling to dl205.md).

Surfaced by the doc audit; no content changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/README.md

@@ -95,6 +95,9 @@ Design decisions + phase plans + execution notes. Load-bearing cross-references
 - [v2/driver-specs.md](v2/driver-specs.md) — per-driver addressing + quirks for every shipped protocol
 - [v2/dev-environment.md](v2/dev-environment.md) — dev-box bootstrap
 - [v2/test-data-sources.md](v2/test-data-sources.md) — integration-test simulator matrix (includes the pinned libplctag `ab_server` version for AB CIP tests)
+- [v2/multi-host-dispatch.md](v2/multi-host-dispatch.md) — per-PLC circuit breakers (Phase 6.1 decision #144)
+- [v2/v2-release-readiness.md](v2/v2-release-readiness.md) — release-readiness tracker
+- [v2/lmx-followups.md](v2/lmx-followups.md) — historical Galaxy-bridge follow-ups (pre-PR-7.2)
 - [v2/implementation/phase-*-*.md](v2/implementation/) — per-phase execution plans with exit-gate evidence
 
 ## v1 archive