nmt-upgrade — update to the latest canon + skills

Installed-suite Canon anchor. When this Skill is installed with the full suite, the bundled Canon is available at ../nmt-chat/references/Next-Move-Theory-Canon/. This packaging pointer does not change the Legacy updater's project-root target.

Re-runs the official Next Move Theory installer from the project root. The installer clones the public repo (zamesin/Next-Move-Theory-Canon-and-Skills, branch main) and refreshes, in place:

• Next-Move-Theory-Canon/ — the canon
• .claude/skills/nmt-* — Claude skills (invoke with /nmt-…)
• .agents/skills/nmt-* — Codex skills (invoke with $nmt-…)
• the <!-- Next-Move-Theory-Rules:start … end --> block in CLAUDE.md and AGENTS.md
• NextMoveTheory-README.md