Summary\n- Adds auth-rca-improvements.md synthesizing all RCA files under ~/Downloads/rca/.\n- Clusters recurring auth failures and proposes fixes across Mercury auth structure, auth linting/CI, and the Cortex config-gen agent.\n- Ranks improvements by impact × effort and recommends PR split across Mercury/Integrator/Hermes follow-ups.\n\nRefs MER-43.\n\n## Validation\n- git diff --check\n- npm run typecheck (fails: package.json has no typecheck script)\n- npm run lint (fails: package.json has no lint script)\n- npm test (fails: package.json has no test script)