SCENARIOS, CHAIN_DEFS and the Scenario type are pure data with no
reactive inputs, but the session controller needs them — leaving them in
the page would mean threading the catalogue through as a dependency.
drillScenarios/chainGroups were computed() over module constants only, so
they can never invalidate; they become plain DRILL_SCENARIOS/CHAIN_GROUPS
consts, evaluated once at module load. Verified the derived shape is
unchanged: 15 scenarios, 2 drills, 3 chains with 4/4/3 segments.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
