semi implemented and features implemented save checkpoint

docs/features/unchecked/cli/cli-reachability-trace-export.md

@@ -0,0 +1,28 @@
+# CLI Reachability Trace Export
+
+## Module
+Cli
+
+## Status
+IMPLEMENTED
+
+## Description
+New stella reachability trace command with flags for scan ID, output format (GraphSON/JSON), runtime-confirmed filtering, minimum score threshold, and deterministic output.
+
+## Implementation Details
+- **Command Group**: `src/Cli/StellaOps.Cli/Commands/ReachabilityCommandGroup.cs` -- `ReachabilityCommandGroup` for reachability commands
+- **ReachGraph Commands**: `src/Cli/StellaOps.Cli/Commands/ReachGraph/ReachGraphCommandGroup.cs` -- reachability graph operations
+- **ReachGraph Handlers**: `src/Cli/StellaOps.Cli/Commands/ReachGraph/ReachGraphCommandHandlers.cs`
+- **Tests**: `src/Cli/__Tests/StellaOps.Cli.Tests/ReachabilityTraceExportCommandTests.cs`
+- **Commands**:
+  - `stella reachability trace --scan <scan-id>` -- export reachability trace. Options: `--format graphson|json`, `--runtime-only` (confirmed only), `--min-score <threshold>`, `--output <path>`
+- **Determinism**: Output is deterministically ordered for reproducible results
+
+## E2E Test Plan
+- [ ] Run `stella reachability trace --scan <id> --format json` and verify JSON trace export
+- [ ] Run `stella reachability trace --scan <id> --format graphson` and verify GraphSON output
+- [ ] Run `stella reachability trace --scan <id> --runtime-only` and verify only runtime-confirmed paths
+- [ ] Run `stella reachability trace --scan <id> --min-score 0.7` and verify score filtering
+- [ ] Verify output is deterministic (same scan produces byte-identical output)
+- [ ] Verify `--output` flag writes to file instead of stdout
+- [ ] Verify error handling for non-existent scan IDs