Add Wave contract schemas for pipeline validation

JSON Schema definitions for all pipeline handover contracts
including issue analysis, research, enhancement, and sync flows.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.wave/contracts/refactor-analysis.schema.json

@@ -0,0 +1,27 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "type": "object",
+  "required": ["target_files", "affected_callers", "existing_tests", "integration_points", "risk_assessment"],
+  "properties": {
+    "target_files": {
+      "type": "array",
+      "items": { "type": "string" }
+    },
+    "affected_callers": {
+      "type": "array",
+      "items": { "type": "string" }
+    },
+    "existing_tests": {
+      "type": "array",
+      "items": { "type": "string" }
+    },
+    "integration_points": {
+      "type": "array",
+      "items": { "type": "string" }
+    },
+    "risk_assessment": {
+      "type": "string",
+      "enum": ["low", "medium", "high"]
+    }
+  }
+}