VU-1134: replace agent eval harness with tiered OpenCode runner

[hbanerjee74]

Fixes VU-1134

Summary

• Replaced the app-local Claude-specific Promptfoo harness with a root tests/evals OpenCode/Promptfoo harness adapted from the migration-utility pattern.
• Added suite-level eval tier/runtime configuration, deterministic contract tests, repo-local Promptfoo state handling, and worktree Promptfoo DB symlinking.
• Removed the old app/agent-tests/promptfoo provider/config path and routed existing smoke commands through the new harness.
• Added release/docs/CI follow-up work: deterministic release-stage and help-doc checkers, refreshed user guide pages, fixed release resource packaging, and made PR CI cheaper through targeted policy checks.
• Updated README, AGENTS, CLAUDE, TEST_MANIFEST, repo-map, Dependabot, and policy workflows for the new eval and CI shape.

Validation

• cd tests/evals && npm test
• node --test scripts/*.test.mjs && node scripts/check-help-docs.mjs
• bash app/scripts/lint-agent-docs.sh
• Workflow YAML parse for .github/workflows/*.yml
• node -e "JSON.parse(require('fs').readFileSync('repo-map.json','utf8')); console.log('repo-map json ok')"
• cd docs && npm ci && npm run build
• npx markdownlint-cli2 "README.md" "AGENTS.md" "CLAUDE.md" "TEST_MANIFEST.md" ".claude/rules/**/*.md" "docs/user-guide/**/*.md" "docs/superpowers/**/*.md"
• cd app && npx tsc --noEmit
• git diff --check origin/main...HEAD

PR phase gates

• AC gate: pass. VU-1134 uses bullet ACs rather than checkboxes; all listed ACs are covered by committed work and validation above.
• Design conformance: not_applicable. Linear issue has no linked local design document or attachment.
• Promptfoo live evals: skipped by policy. Live/model-backed smoke commands are documented as manual and should be run by the user after selecting the target model.

Manual follow-up

After selecting the target model/runtime, run the live smoke command manually:

cd app && npm run test:agents:smoke

[linear-code]

VU-1134 Replace agent eval harness with migration-utility tiered runner