Prepare Evident v0.1.0 release

[hudsonaikins]

Summary

• add v0.1.0 changelog and getting-started adoption guide
• add Codex review guide and consumer workflow example
• update reusable workflow so consumer repos can fetch the Evident toolkit when scripts are not vendored
• add agentic tooling stack docs covering Code Storage, Entire, Graphite, GitHub, Codex, and Evident boundaries
• add README badges/stack tags and package keywords for Graphite, Entire, Code Storage, stacked PRs, and Codex
• ignore generated evident-pr-evidence.json

Validation

• npm run check
• node --check scripts/check-evident-evidence-envelope.mjs && node --check scripts/check-evident-external-actions.mjs && node --check scripts/write-evident-evidence-envelope.mjs
• generated evidence validation with /tmp/evident-pr-evidence.json
• npx --yes ajv-cli@5 validate --spec=draft2020 -s schemas/evidence-envelope.schema.json -r schemas/external-action-policy.schema.json -d examples/evident-evidence/minimal-evidence.json
• /tmp/actionlint-v1.7.12/actionlint
• Fallow changed-code audit: pass
• git diff --check