Drop cq- prefix from plugin command filenames

[peteski22]

Summary

• Rename plugins/cq/commands/cq-reflect.md → reflect.md and cq-status.md → status.md so slash commands resolve as /cq:reflect and /cq:status instead of the double-prefixed /cq:cq-* forms.
• Align OpenCode install test fixtures with the new layout.
• Refresh directory diagrams in docs/CQ-Proposal.md and docs/plans/2026-03-04-craic-mvp-poc-design.md.

Closes #295

Release note (required)

The installer writes command files into user-managed target dirs (.opencode/commands/ for OpenCode; Claude Code's plugin cache is rewritten by the Claude CLI on plugin sync and is not affected). After this rename, the old cq-reflect.md / cq-status.md files left behind by prior OpenCode installs will not be cleaned up automatically — the uninstaller only knows about files whose names match current plugin sources.

Include the following in the next plugin release notes:

OpenCode users: run cq-install uninstall --target opencode against your existing install before upgrading (or delete <target>/commands/cq-reflect.md and <target>/commands/cq-status.md manually), then reinstall. This clears the legacy double-prefixed command files; otherwise they will linger alongside the new /cq:reflect and /cq:status commands until removed by hand.

Claude Code users and Cursor/Windsurf users are unaffected (Claude Code is managed through the plugin marketplace; Cursor and Windsurf installs never wrote command files).

Test plan

• make lint
• make test
• Refresh local marketplace + plugin cache per issue instructions and verify /cq:reflect and /cq:status resolve in Claude Code.