v0.2.3 — opencode honesty pass

Changed

• installers/opencode.sh no longer claims "opencode wired" on success.
  OpenCode 1.14.48 has no statusline plugin hook — verified by enumerating
  the full event surface in @opencode-ai/plugin's dist/index.d.ts
  (chat.*, tool.execute.*, permission.ask, etc. — all behavioral,
  none render). The installer still writes the proposed config keys
  speculatively so a future upstream ship (tracking
  anomalyco/opencode#8619) auto-activates, but it now prints a clear
  "pending upstream" warning and links the issue so users aren't
  confused when their built-in footer keeps rendering.
• README and AGENTS.md updated to reflect the real opencode status: not
  pending-implementation, but pending-upstream — there's no plugin-side
  workaround that avoids burning context tokens.