Add turn-based intent demo

[rivendale]

Summary

• adds a no-build, browser-only turn-based game demo showing the full pwcli-core loop: command input -> intent telemetry -> registered primitive -> preview/approval -> deterministic ledger -> return focus
• extends primitive.schema.json with optional UX metadata for primary action, preview fields, risk labels, cost fields, state copy, and undo policy
• adds a Human UX guide for Basic / Intermediate / Advanced progressive disclosure and assertion separation
• adds example fixture wrappers and an example-local result ledger schema
• hardens validation for static demo files, example-local schemas, and example fixture schema refs/shapes
• adds public Apache-2.0 rivendale/iocalc-agent-env as a maintainer companion reference; intentionally does not add private iso-ai-game

Review hardening

Two read-only adversarial reviews ran before commit. Findings patched:

• escaped data-bearing strings in the demo before rendering through innerHTML
• rendered risk and cost metadata in the preview panel
• removed structuredClone dependency with a small clone helper
• renamed the demo from domain-specific Season Duel wording to neutral turn-based game language
• removed the local: fixture schema bypass so fixtures must point to real .schema.json files
• clarified validation docs so they do not overstate full JSON Schema validation

Validation

• node --check scripts/validate.mjs
• node --check examples/turn-based-game/demo.js
• npm run validate
• git diff --check