Why: local/opencode was listed as 'missing' in manifest.json — users
could not run OpenCode on their local machine via spawn.
- Add local/opencode.sh following the same pattern as other local scripts
(sources lib/common.sh, uses opencode_install_cmd from shared/common.sh,
injects OPENROUTER_API_KEY via generate_env_config)
- Update manifest.json matrix entry from 'missing' to 'implemented'
Agent: team-lead
Co-authored-by: B <6723574+louisgv@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
