chore: import upstream snapshot with attribution

examples/openai-function-call/README.md

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+# openai-function-call (OpenAI Function Call Example)
+
+You can run this example with:
+
+```bash
+npx promptfoo@latest init --example openai-function-call
+cd openai-function-call
+```
+
+This example demonstrates how to use promptfoo to evaluate OpenAI function calls. It showcases two different methods of defining functions: in an external YAML file and directly in the configuration file.
+
+## Setup
+
+1. Set your OPENAI_API_KEY environment variable:
+
+   ```bash
+   export OPENAI_API_KEY=your_api_key_here
+   ```
+
+2. This example is pre-configured in `promptfooconfig.yaml`. You can review and modify it if needed.
+
+3. Run the evaluation:
+
+   ```bash
+   promptfoo eval
+   ```
+
+4. View the results:
+
+   ```bash
+   promptfoo view
+   ```

examples/openai-function-call/get_current_weather.yaml

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+- name: get_current_weather
+  description: Get the current weather in a given location
+  parameters:
+    type: object
+    properties:
+      location:
+        type: string
+        description: The city and state, e.g. San Francisco, CA
+      unit:
+        type: string
+        enum:
+          - celsius
+          - fahrenheit
+    required:
+      - location

examples/openai-function-call/promptfooconfig.yaml

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+# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
+description: OpenAI function calling with weather API integration
+
+prompts:
+  - 'What is the weather like in {{city}}?'
+
+providers:
+  - id: 'openai:chat:gpt-4.1-mini'
+    label: 'functions-defined-in-external-file'
+    config:
+      functions: file://get_current_weather.yaml
+  - id: 'openai:chat:gpt-4.1-mini'
+    label: 'functions-defined-in-config'
+    config:
+      functions:
+        [
+          {
+            'name': 'get_current_weather',
+            'description': 'Get the current weather in a given location',
+            'parameters':
+              {
+                'type': 'object',
+                'properties':
+                  {
+                    'location':
+                      {
+                        'type': 'string',
+                        'description': 'The city and state, e.g. San Francisco, CA',
+                      },
+                    'unit': { 'type': 'string', 'enum': ['celsius', 'fahrenheit'] },
+                  },
+                'required': ['location'],
+              },
+          },
+        ]
+
+tests:
+  - vars:
+      city: Boston
+    assert:
+      - type: is-json
+      - type: is-valid-openai-function-call
+      - type: javascript
+        value: output.name === 'get_current_weather'
+      - type: javascript
+        value: JSON.parse(output.arguments).location === 'Boston, MA'
+
+  - vars:
+      city: New York
+    assert:
+      - type: equals
+        value: get_current_weather
+        # Transform is a cleaner way to pick out specific properties.
+        # This transform returns only the 'name' property
+        transform: output.name
+      - type: similar
+        value: NYC
+        threshold: 0.5
+        # This transform returns only the parsed location argument.
+        transform: JSON.parse(output.arguments).location
+
+  - vars:
+      city: Paris
+
+  - vars:
+      city: Mars