docs: add Kern release evidence gate

[raymondware]

Summary

• adds lightweight CI for Kern release-evidence validation
• adds docs/smoke-test.md with plugin install, command smoke, fixture recording, and release-ready gates
• aligns public score and phase-count docs to the current 0-100 / 6-phase model

Verification

• python3 tools/validate-release-evidence.py
• bash tests/run-audit-fixtures.sh
• python3 -m json.tool .claude-plugin/plugin.json
• python3 -m json.tool .claude-plugin/marketplace.json
• python3 -m json.tool anti-patterns/manifest.json
• python3 -m json.tool tests/audit-fixtures/manifest.json
• python3 -m json.tool tests/audit-fixtures/results.json
• git diff --check
• targeted changed-file secret-value scan: 0 hits

Guardrails

No release/tag, marketplace mutation, external launch/post, deploy, or main push performed.