Wave 5: Schemas command, sync command, network policy, test fixtures (bd-x15, bd-3f4, bd-1cv, bd-lx6)

- Implement schemas command with list/show modes, regex filtering, ref expansion
- Implement sync command with conditional fetch, content hash diffing, dry-run
- Add NetworkPolicy enum (Auto/Offline/OnlineOnly) with env var + CLI flag resolution
- Integrate network policy into AsyncHttpClient and fetch command
- Create test fixtures (petstore.json/yaml, minimal.json) and integration test helpers
- Fix clippy lints: derivable_impls, len_zero, borrow-after-move, deprecated API
- 192 tests passing (179 unit + 13 integration), all quality gates green

tests/fixtures/minimal.json

@@ -0,0 +1,92 @@
+{
+  "openapi": "3.0.3",
+  "info": {
+    "title": "Minimal API",
+    "version": "0.1.0"
+  },
+  "paths": {
+    "/items": {
+      "get": {
+        "operationId": "listItems",
+        "summary": "List items",
+        "responses": {
+          "200": {
+            "description": "A list of items",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/ItemList" }
+              }
+            }
+          }
+        }
+      },
+      "post": {
+        "operationId": "createItem",
+        "summary": "Create item",
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": { "$ref": "#/components/schemas/Item" }
+            }
+          }
+        },
+        "responses": {
+          "201": {
+            "description": "Item created",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/Item" }
+              }
+            }
+          }
+        }
+      }
+    },
+    "/items/{id}": {
+      "get": {
+        "operationId": "getItem",
+        "summary": "Get item by ID",
+        "parameters": [
+          {
+            "name": "id",
+            "in": "path",
+            "required": true
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "A single item",
+            "content": {
+              "application/json": {
+                "schema": { "$ref": "#/components/schemas/Item" }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "Item": {
+        "type": "object",
+        "required": ["id", "name"],
+        "properties": {
+          "id": { "type": "integer", "format": "int64" },
+          "name": { "type": "string" }
+        }
+      },
+      "ItemList": {
+        "type": "object",
+        "properties": {
+          "items": {
+            "type": "array",
+            "items": { "$ref": "#/components/schemas/Item" }
+          },
+          "total": { "type": "integer" }
+        }
+      }
+    }
+  }
+}