#3345 Docs: state the OpenCode version requirement for the swamp audit plugin

swamp-club#3340 changes the managed OpenCode audit plugin (.opencode/plugins/swamp-audit.ts) so it loads on OpenCode 2 as well as OpenCode 1. The new file needs OpenCode 1.3.4 or later, or OpenCode 2. On OpenCode 1.0 to 1.2.10 the new file crashes OpenCode runs, and on 1.2.11 to 1.3.3 it records commands but OpenCode shows a Failed to load plugin error. OpenCode only installs patch releases automatically, so users on those older minor lines stay there until they update OpenCode themselves.

The manual does not state any OpenCode version requirement today. content/manual/reference/repository-configuration.md lists .opencode/plugins/swamp-audit.ts in the per-tool table (the opencode row) without a version.

Suggested change: next to the opencode row (or in a note under the table), say that the OpenCode audit plugin requires OpenCode 1.3.4 or later, or OpenCode 2, and that users on older OpenCode 1 builds should update OpenCode before running swamp repo upgrade. If the doctor reference (doctor.md) lists the agent-config-loadable check per tool, mention that it fails on an OpenCode plugin written before OpenCode 2 support and names the version requirement in its hint.

Land this alongside the release that ships swamp-club#3340.