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/feature-plan.schema.json

@@ -0,0 +1,33 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "Feature Implementation Plan",
+  "description": "Ordered implementation plan for a feature",
+  "type": "object",
+  "required": ["feature", "steps", "total_complexity", "timestamp"],
+  "properties": {
+    "feature": { "type": "string", "minLength": 5 },
+    "steps": {
+      "type": "array",
+      "minItems": 1,
+      "items": {
+        "type": "object",
+        "required": ["id", "title", "description"],
+        "properties": {
+          "id": { "type": "string", "pattern": "^S\\d{2}$" },
+          "title": { "type": "string" },
+          "description": { "type": "string" },
+          "files_to_modify": { "type": "array", "items": { "type": "string" } },
+          "files_to_create": { "type": "array", "items": { "type": "string" } },
+          "tests_to_write": { "type": "array", "items": { "type": "string" } },
+          "acceptance_criteria": { "type": "array", "items": { "type": "string" } },
+          "complexity": { "type": "string", "enum": ["S", "M", "L"] },
+          "dependencies": { "type": "array", "items": { "type": "string" } }
+        }
+      }
+    },
+    "total_complexity": { "type": "string", "enum": ["S", "M", "L", "XL"] },
+    "branch_name_suggestion": { "type": "string" },
+    "commit_message_suggestion": { "type": "string" },
+    "timestamp": { "type": "string", "format": "date-time" }
+  }
+}