Add integration tests for Proof Chain and Reachability workflows

- Implement ProofChainTestFixture for PostgreSQL-backed integration tests.
- Create StellaOps.Integration.ProofChain project with necessary dependencies.
- Add ReachabilityIntegrationTests to validate call graph extraction and reachability analysis.
- Introduce ReachabilityTestFixture for managing corpus and fixture paths.
- Establish StellaOps.Integration.Reachability project with required references.
- Develop UnknownsWorkflowTests to cover the unknowns lifecycle: detection, ranking, escalation, and resolution.
- Create StellaOps.Integration.Unknowns project with dependencies for unknowns workflow.

src/Cli/StellaOps.Cli/Commands/CommandHandlers.Witness.cs

@@ -146,8 +146,9 @@ internal static partial class CommandHandlers
     internal static async Task HandleWitnessListAsync(
         IServiceProvider services,
         string scanId,
-        string? cve,
+        string? vuln,
         string? tier,
+        bool reachableOnly,
         string format,
         int limit,
         bool verbose,
@@ -158,8 +159,9 @@ internal static partial class CommandHandlers
         if (verbose)
         {
             console.MarkupLine($"[dim]Listing witnesses for scan: {scanId}[/]");
-            if (cve != null) console.MarkupLine($"[dim]Filtering by CVE: {cve}[/]");
+            if (vuln != null) console.MarkupLine($"[dim]Filtering by vuln: {vuln}[/]");
             if (tier != null) console.MarkupLine($"[dim]Filtering by tier: {tier}[/]");
+            if (reachableOnly) console.MarkupLine("[dim]Showing reachable witnesses only[/]");
         }
 
         // TODO: Replace with actual service call