feat(init): warn-only ESLint config; enforcement via ratchet

[mojoatomic]

Simplify onboarding to passive start by making init generate warn-only ESLint config and deferring enforcement to ratchet.

Changes

• Generator: lib/generators/eslint-config.js now emits warn-only severities for built-in rules (no-undef, no-var, eqeqeq, camelcase)
• Architecture generator: CLI max-lines override switched to warn (enforcement handled via ratchet/baseline), test updated accordingly

Why

• Avoids CI breakage during initial adoption; ESLint is measurement, ratchet handles enforcement.
• Aligns with permissive-start + progressive ratchet docs (Health Gating Enforcement for Context-Aware Ratchet #203/Docs: health gating troubleshooting + calibration guide (#203 follow-up) #215)

Behavior

• init produces eslint.config.mjs with all warnings
• CI stays green; ratchet enforces regressions and locked rules

Tests

• Updated eslint-arch-config.test for warn-only CLI override; suite is green.