# SBOM Graph Reachability Overlay with Time Slider

## Module
Web

## Status
IMPLEMENTED

## Description
Reachability halo overlay on SBOM graph visualization with time slider for temporal reachability exploration and state legend. Uses deterministic stub data pending fixture bundle.

## What's Implemented
- **Existing components**:
  - `graph-canvas` (`src/Web/StellaOps.Web/src/app/features/graph/graph-canvas.component.ts`)
  - `graph-explorer` (`src/Web/StellaOps.Web/src/app/features/graph/graph-explorer.component.ts`)
  - `graph-filters` (`src/Web/StellaOps.Web/src/app/features/graph/graph-filters.component.ts`)
  - `graph-hotkey-help` (`src/Web/StellaOps.Web/src/app/features/graph/graph-hotkey-help.component.ts`)
  - `graph-overlays` (`src/Web/StellaOps.Web/src/app/features/graph/graph-overlays.component.ts`)
  - `graph-side-panels` (`src/Web/StellaOps.Web/src/app/features/graph/graph-side-panels.component.ts`)
- **Existing services**:
  - `graph-accessibility` (`src/Web/StellaOps.Web/src/app/features/graph/graph-accessibility.service.ts`)

## What's Missing
- **Reachability halo overlay**: Graph overlay components exist but no dedicated reachability state halo (color-coded rings around nodes showing lattice state: SR/SU/RO/RU/CR/CU/X)
- **Time slider for temporal reachability**: No time slider component enabling temporal exploration of how reachability states evolved over scan/signal events
- **Lattice state legend**: No legend component mapping halo colors to reachability lattice states
- **Backend API for temporal reachability**: No API endpoint returning reachability state snapshots at different points in time
- **Deterministic fixture bundle**: Currently uses stub data; pending fixture bundle with real reachability overlay data

## Implementation Plan
- Add reachability state halo overlay to graph-overlays component using lattice state colors
- Create time slider component for temporal reachability exploration
- Add lattice state legend component
- Build backend API for temporal reachability snapshots
- Wire overlay to live reachability data via graph service

## E2E Test Plan
- **Setup**:
  - [ ] Log in with a user that has appropriate permissions
  - [ ] Navigate to `/graph`
  - [ ] Ensure test data exists (scanned artifacts, SBOM data, or seed data as needed)
- **Core verification**:
  - [ ] Verify the visualization renders correctly with sample data
  - [ ] Verify interactive elements (hover tooltips, click-to-drill-down) work
  - [ ] Verify the visualization handles empty/minimal data gracefully
- **Edge cases**:
  - [ ] Verify graceful handling when backend API is unavailable (error state)
  - [ ] Verify responsive layout at different viewport sizes
  - [ ] Verify accessibility (keyboard navigation, screen reader labels, ARIA attributes)