refactor(go): split portfolio, workshop, training/models, roadmap stores
portfolio/store.go (818 LOC) → store_portfolio.go, store_items.go, store_metrics.go
workshop/store.go (793 LOC) → store_sessions.go, store_participants.go, store_responses.go
training/models.go (757 LOC) → models_enums.go, models_core.go, models_api.go, models_blocks.go
roadmap/store.go (757 LOC) → store_roadmap.go, store_items.go, store_import.go
All files under 350 LOC. Zero behavior changes, same package declarations.
go vet passes on all five packages.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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