Fix RenderWorkflow() handler (was a stub that never loaded data),
remove dead chat UI from workflow.html, align stage mode naming
with Go constants, add 17 SQLite store tests, decompose 400-line
InstallPackage into 7 phases, add E2E workflow-without-chat test.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
