semi implemented and features implemented save checkpoint

docs/features/unchecked/scanner/runtime-timeline-api.md

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+# Runtime Timeline API
+
+## Module
+Scanner
+
+## Status
+IMPLEMENTED
+
+## Description
+Provides a chronological timeline of runtime observations (RuntimeTimeline model, TimelineBuilder, RuntimePosture enum) with an API endpoint. Distinct from "Runtime Reachability Collection" which is about gathering data, not the timeline visualization API.
+
+## Implementation Details
+- **Timeline Model**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Analyzers.Native/RuntimeCapture/Timeline/RuntimeTimeline.cs` - `RuntimeTimeline` model representing a chronological sequence of runtime observations with `RuntimePosture` classification
+- **Timeline Builder**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Analyzers.Native/RuntimeCapture/Timeline/TimelineBuilder.cs` - `TimelineBuilder` constructs timeline instances from raw runtime observations, ordering events chronologically and computing posture
+- **Tests**:
+  - `src/Scanner/__Tests/StellaOps.Scanner.Analyzers.Native.Library.Tests/RuntimeCapture/Timeline/TimelineBuilderTests.cs` - Unit tests for timeline construction and posture computation
+
+## E2E Test Plan
+- [ ] Build a runtime timeline from a set of native runtime observations and verify events are ordered chronologically
+- [ ] Verify the `RuntimePosture` enum correctly classifies the overall runtime posture based on observation patterns
+- [ ] Verify timeline entries include observation timestamps, source types, and observation counts
+- [ ] Submit runtime observations over time and verify the timeline reflects the temporal progression accurately
+- [ ] Verify the timeline API endpoint returns the timeline in a serializable format with correct pagination support