`extract` reports extraction errors / exits with code 1 for APIs using `set-body template="liquid"` with `{{ }}` expressions

### Command that triggered the bug

apiops extract --log-level debug --resource-group --service-name --output ./artifacts --filter ./configuration.extractor.yaml --subscription-id --remove-stale

### Expected behavior

Extraction completes with exit code 0 for an API whose policy uses `set-body template="liquid"` to build or transform a request/response body, as long as the API and its real named values/backends actually exist and are reachable.

### Actual behavior

The extraction otherwise finishes fine. All APIs, operations, and real named values get written to the output directory. But the run still reports errors and exits with code 1:

```
[INFO] Extraction complete: 19 resources extracted, 4 errors
```

With `--log-level debug` on, I can see the CLI issuing `GET .../namedValues/` requests where `` isn't a named value at all. It looks like it was pulled straight out of a `{{ ... }}` expression inside one of our `set-body template="liquid">` blocks:

```
[DEBUG] HTTP GET https://management.azure.com/.../namedValues/context.Request.MatchedParameters%5B%22id%22%5D?api-version=2025-09-01-preview
[DEBUG] HTTP GET https://management.azure.com/.../namedValues/body.envelope.body.Test_Result.test?api-version=2025-09-01-preview
[DEBUG] HTTP GET https://management.azure.com/.../namedValues/body.envelope.body.fault.faultcode?api-version=2025-09-01-preview
[DEBUG] HTTP GET https://management.azure.com/.../namedValues/body.envelope.body.fault.faultstring?api-version=2025-09-01-preview
```

None of those are named values in our APIM instance. They're Liquid interpolation expressions from a `set-body template="liquid"` policy we use to build a SOAP request and reshape the SOAP response into JSON. Each lookup 404s, and each 404 seems to get counted toward the "errors" total. That matches up exactly: 4 Liquid expressions, 4 reported errors. The nonzero exit code then fails our CI pipeline step even though nothing is actually broken or missing.

To work around this we rewrote the affected `set-body template="liquid">` blocks as plain C# expressions (`@{ ... return ...; }`) instead of Liquid templates. That removed the `{{ }}` syntax from the policy entirely, and the same extraction now completes with 0 errors and exit code 0. But with the Liquid template the policy would be easier to read and understand.

### apiops CLI version

1.0.1

### Environment details

- Azure DevOps pipeline, Ubuntu 24.04 hosted agent
- Node.js 24.x
- `apiops extract` invoked via `npx`, with `--filter` pointing at a YAML filter config
- The affected API's policy has three `` blocks: one building a SOAP request body (interpolating a template parameter), and two transforming the SOAP response into JSON (interpolating values pulled out of the parsed SOAP envelope)

### CI/CD environment

Azure DevOps

### Is this bug blocking you?

No

Start by running the reported `apiops extract` command against an API policy containing `set-body template="liquid"` with `{{ }}` expressions, using debug logging to trace the named-value lookups. Follow the extraction path that parses policy expressions and verify that Liquid expressions are not treated as named values. Done means the extraction reports zero errors and exits with code 0 when the referenced API resources are valid.

Scritto dal modello di indicizzazione a partire dal testo della issue.