The intraday chart data builder lived inside dashboard-utils with observation-source and TAF helpers, so chart consumers had to depend on the large dashboard utility surface. This moves chart data preparation, observation-source helpers, and TAF marker labels into focused modules while keeping dashboard-utils re-export compatibility.
Constraint: Preserve existing chart data shape, observation labels, TAF labels, and legacy dashboard-utils exports.
Rejected: Rewrite chart data generation while moving it | this pass is a boundary move only so visual behavior remains stable.
Confidence: high
Scope-risk: moderate
Reversibility: clean
Tested: TypeScript diagnostics for chart-utils, dashboard-utils, observation-source-utils, and taf-utils
Tested: npm run build
Not-tested: Browser visual regression across every chart city.
City decision cards rendered Chart.js canvases and AI evidence bodies before the user could see or expand those sections. This keeps the card shell visible while delaying chart data/canvas work until the section nears the viewport and skipping the AI evidence body while its details panel is collapsed.
Constraint: Preserve existing decision-card layout and evidence copy.
Rejected: Add list virtualization in the same pass | card-level render costs should be reduced before changing list mechanics.
Confidence: high
Scope-risk: narrow
Reversibility: clean
Tested: npm run build
Not-tested: Runtime scroll benchmark on a large production city set.
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