Add signal contracts for reachability, exploitability, trust, and unknown symbols

- Introduced `ReachabilityState`, `RuntimeHit`, `ExploitabilitySignal`, `ReachabilitySignal`, `SignalEnvelope`, `SignalType`, `TrustSignal`, and `UnknownSymbolSignal` records to define various signal types and their properties.
- Implemented JSON serialization attributes for proper data interchange.
- Created project files for the new signal contracts library and corresponding test projects.
- Added deterministic test fixtures for micro-interaction testing.
- Included cryptographic keys for secure operations with cosign.

.claude/settings.local.json

@@ -20,9 +20,14 @@
       "Bash(src/Cli/StellaOps.Cli/Telemetry/TraceparentHttpMessageHandler.cs)",
       "Bash(python3:*)",
       "Bash(dotnet list:*)",
-      "WebSearch"
+      "WebSearch",
+      "Bash(find:*)",
+      "Bash(xargs:*)",
+      "Bash(ls:*)",
+      "Bash(mkdir -p:*)"
     ],
     "deny": [],
     "ask": []
-  }
+  },
+  "outputStyle": "default"
 }