feat: add governed State Management domain

[changeroa]

Summary

• add an experimental, framework-neutral State Management domain with a planning workflow, decision tree, brief, verification matrix, six patterns, and three recipes
• wire the sixth domain through repository IA, governance, ownership, vocabulary, quality routing, and regression validators
• extend Material v2 discovery, identity, admission, CLI/MCP resources, and package exposure from 126 to 144 admitted materials
• replace the five-domain README infographic with a six-domain version

Verification

• npm run test:material
• npm test
• domain, IA, OKF, governance, link, and Consumer Reference validation suites
• Material CLI and MCP discovery: 6 domains and 144 resources
• git diff --cached --check