Reusable puppeteer model (tests/browser/) following the existing tests/performance/chrome-devtools-test.mjs conventions. ACSession drives a single local Chrome against a live URL (default production, override via AC_TEST_URL) — type/press/drag/screenshot/state — plus a dependency-free scenario()/report() runner. prompt.mjs gains a read-only window.__acPromptTest() snapshot gated on window.acDEBUG so canvas UI is assertable; degrades to screenshot-only when the hook is absent. Scenarios: boot, sigil $, universal bare-word (color-typed), Enter discipline + Tab-complete, rolodex drag, UNITICKER deprecation. npm run test:browser[:headed|:local]; screenshots gitignored. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>