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/issue-impl-plan.schema.json

@@ -0,0 +1,72 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "Issue Implementation Plan",
+  "type": "object",
+  "required": ["issue_number", "branch_name", "feature_dir", "tasks"],
+  "properties": {
+    "issue_number": {
+      "type": "integer",
+      "minimum": 1
+    },
+    "branch_name": {
+      "type": "string",
+      "minLength": 1
+    },
+    "feature_dir": {
+      "type": "string",
+      "description": "Path to the feature directory under specs/"
+    },
+    "spec_file": {
+      "type": "string",
+      "description": "Path to the spec.md file"
+    },
+    "plan_file": {
+      "type": "string",
+      "description": "Path to the plan.md file"
+    },
+    "tasks_file": {
+      "type": "string",
+      "description": "Path to the tasks.md file"
+    },
+    "tasks": {
+      "type": "array",
+      "minItems": 1,
+      "items": {
+        "type": "object",
+        "required": ["id", "title", "description"],
+        "properties": {
+          "id": {
+            "type": "string",
+            "description": "Task identifier"
+          },
+          "title": {
+            "type": "string",
+            "description": "Brief task title"
+          },
+          "description": {
+            "type": "string",
+            "description": "Detailed task description"
+          },
+          "file_changes": {
+            "type": "array",
+            "items": {
+              "type": "object",
+              "required": ["path", "action"],
+              "properties": {
+                "path": { "type": "string" },
+                "action": {
+                  "type": "string",
+                  "enum": ["create", "modify", "delete"]
+                }
+              }
+            }
+          }
+        }
+      }
+    },
+    "summary": {
+      "type": "string",
+      "description": "Brief summary of the implementation plan"
+    }
+  }
+}