feat: bootstrap design kit and vaporwave demo baseline

kit/patterns/timeline-cards/contract.md

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+# Contract: Timeline Cards + Drilldown
+
+## Card Grouping
+
+- Render timeline as grouped cards (typically by day), not raw event rows.
+- Correlated or visually equivalent events may be collapsed into one card with counts.
+- Card summaries should be human-readable and avoid repeating page-scope identity labels.
+
+## Filters
+
+- Timeline filters are server-side when timeline is paginated or large.
+- Filters should preserve grouping semantics and timezone behavior.
+- Scope-invariant filters may be hidden on entity detail pages.
+
+## Drilldown
+
+- One card opens one drilldown modal/panel.
+- Drilldown contains:
+  - event list (left/top)
+  - selected event details (right/bottom)
+- No nested modal inside drilldown.
+- Card-local search/filter may be applied within the drilldown.
+
+## UX Rules
+
+- Use human-readable source labels.
+- Prefer action-oriented card titles (`Installed N components`, `Removed N components`).
+- Empty states must explain whether filters removed all results.
+