chore: import upstream snapshot with attribution

examples/eval-json-output/README.md

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+# eval-json-output (Json Output)
+
+You can run this example with:
+
+```bash
+npx promptfoo@latest init --example eval-json-output
+cd eval-json-output
+```
+
+## Usage
+
+To get started, set your OPENAI_API_KEY environment variable.
+
+Next, edit promptfooconfig.yaml.
+
+Then run:
+
+```bash
+promptfoo eval
+```
+
+Afterwards, you can view the results by running `promptfoo view`

examples/eval-json-output/promptfooconfig.yaml

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+# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
+description: 'JSON object evals'
+
+prompts:
+  - 'Output a JSON object that contains the keys `color` and `countries`, describing the following object: {{item}}'
+
+providers:
+  - id: openai:chat:gpt-4.1-mini
+    config:
+      response_format:
+        type: json_object
+
+tests:
+  - vars:
+      item: Banana
+    assert:
+      - type: is-json
+      - type: javascript
+        # Parse the JSON and test the contents
+        value: JSON.parse(output).color === 'yellow' && JSON.parse(output).countries.includes('Ecuador')
+
+  - vars:
+      item: Passion fruit
+    options:
+      # Parse the JSON before all assertions
+      transform: JSON.parse(output)
+    assert:
+      - type: is-json
+        # Optional JSON schema
+        value:
+          required:
+            - 'color'
+            - 'countries'
+          type: object
+          properties:
+            color:
+              type: string
+            countries:
+              type: array
+              items:
+                type: string
+      - type: javascript
+        # JSON.parse is no longer necessary here
+        value: output.color === 'purple' && output.countries.includes('Brazil')
+      - type: contains-any
+        transform: output.countries
+        value:
+          - Guatemala
+          - Costa Rica
+          - India
+          - Indonesia
+# Uncomment to parse JSON outputs for ALL tests
+# defaultTest:
+#   options:
+#     transform: JSON.parse(output)