semi implemented and features implemented save checkpoint

docs/features/unchecked/excititor/excititor-vex-evidence-chunk-service.md

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+# Excititor VEX Evidence Chunk Service
+
+## Module
+Excititor
+
+## Status
+IMPLEMENTED
+
+## Description
+Chunked evidence service for VEX data that splits large evidence payloads into manageable chunks for API transport and storage.
+
+## Implementation Details
+- **Modules**: `src/Excititor/StellaOps.Excititor.WebService/Services/`, `src/Excititor/StellaOps.Excititor.WebService/Endpoints/`
+- **Key Classes**:
+  - `VexEvidenceChunkService` (`src/Excititor/StellaOps.Excititor.WebService/Services/VexEvidenceChunkService.cs`) - splits large VEX evidence payloads into chunks for transport
+  - `EvidenceEndpoints` (`src/Excititor/StellaOps.Excititor.WebService/Endpoints/EvidenceEndpoints.cs`) - REST endpoints for evidence chunk operations
+  - `VexEvidenceChunkContracts` (`src/Excititor/StellaOps.Excititor.WebService/Contracts/VexEvidenceChunkContracts.cs`) - API contracts for evidence chunks
+  - `VexEvidenceContracts` (`src/Excititor/StellaOps.Excititor.WebService/Contracts/VexEvidenceContracts.cs`) - API contracts for evidence data
+- **Interfaces**: None (uses concrete service)
+- **Source**: Sprints 0119 (batch_14/file_19.md)
+
+## E2E Test Plan
+- [ ] Submit a large VEX evidence payload and verify `VexEvidenceChunkService` splits it into chunks within size limits
+- [ ] Retrieve chunked evidence via `EvidenceEndpoints` and verify all chunks can be reassembled into the original payload
+- [ ] Verify chunk ordering is preserved and each chunk includes a sequence number
+- [ ] Verify `VexEvidenceChunkContracts` response includes chunk count and total size metadata
+- [ ] Verify chunked transport handles partial failures gracefully (retry individual chunks)
+- [ ] Verify large evidence payloads (>10MB) are chunked without memory issues