chore: import upstream snapshot with attribution

examples/eval-javascript-assert-params/README.md

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+# eval-javascript-assert-params (JavaScript Assertion Params)
+
+## What this demonstrates
+
+Prototype for comparing two ways to parameterize `type: javascript` assertions.
+
+The recommended pattern uses assertion-local `config` values and reads them from
+`context.config` inside the JavaScript assertion. That keeps prompt/test vars
+focused on prompt rendering data and allows the same assertion script to run
+with different parameters in the same test case.
+
+## Environment Variables
+
+No environment variables are required to run this example.
+
+```bash
+npx promptfoo@latest init --example eval-javascript-assert-params
+cd eval-javascript-assert-params
+```
+
+Run the config-based version:
+
+```bash
+promptfoo eval -c promptfooconfig.yaml --no-cache
+```
+
+Run the test-vars workaround version for comparison:
+
+```bash
+promptfoo eval -c promptfooconfig.test-vars.yaml --no-cache
+```

examples/eval-javascript-assert-params/assert-length.js

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+module.exports = (output, context) => {
+  const minLength = context.config?.minLength;
+  if (typeof minLength !== 'number') {
+    throw new Error('Expected assertion config.minLength to be a number');
+  }
+
+  const actualLength = output.length;
+
+  return {
+    pass: actualLength >= minLength,
+    score: actualLength,
+    reason: `Output length ${actualLength} vs minLength ${minLength}`,
+  };
+};

examples/eval-javascript-assert-params/promptfooconfig.test-vars.yaml

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+# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
+description: JavaScript assertion params via test vars
+
+prompts:
+  - '{{reply}}'
+
+providers:
+  - echo
+
+tests:
+  - description: Test-wide vars force assertion-specific param names
+    vars:
+      reply: hello world from promptfoo
+      shortMinLength: 5
+      longMinLength: 20
+    assert:
+      - type: javascript
+        value: output.length >= context.vars.shortMinLength
+      - type: javascript
+        value: output.length >= context.vars.longMinLength

examples/eval-javascript-assert-params/promptfooconfig.yaml

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+# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
+description: JavaScript assertion params via config
+
+prompts:
+  - '{{reply}}'
+
+providers:
+  - echo
+
+tests:
+  - description: Same script, two assertion-local parameter sets
+    vars:
+      reply: hello world from promptfoo
+    assert:
+      - type: javascript
+        value: file://assert-length.js
+        config:
+          minLength: 5
+      - type: javascript
+        value: file://assert-length.js
+        config:
+          minLength: 20