[test-improver] Improve tests for httputil package

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File Analyzed

• Test File: internal/httputil/httputil_test.go
• Package: internal/httputil
• Lines of Code: 140 → 153

Improvements Made

1. Increased Coverage

• ✅ Added test for the previously-uncovered json.Marshal error path in WriteJSONResponse

The WriteJSONResponse function commits response headers before attempting to marshal the body:

func WriteJSONResponse(w http.ResponseWriter, statusCode int, body interface{}) {
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(statusCode)          // ← headers committed here
    data, err := json.Marshal(body)
    if err != nil {
        return                         // ← this branch was untested
    }
    w.Write(data)
}
```

The new test passes a `chan int` (which `json.Marshal` cannot encode) to exercise the `return` branch and documents the observable side-effects: `Content-Type` and status code are already written, but the response body is empty.

### 2. Documents Important Behavior

The test makes explicit a subtle contract: callers should not rely on a body being present when passing exotic types, even though the status code will always be written. This is useful context for future maintainers.

## Test Output

All existing tests continue to pass; the new subtest name is:

```
--- PASS: TestWriteJSONResponse/unmarshalable_body_writes_headers_but_no_body

Why These Changes?

httputil is a shared utility used across the server and proxy packages. Its only function had one branch (if err != nil { return }) that was never exercised. A chan int is the canonical Go type that is always rejected by json.Marshal, making this a clean, dependency-free way to cover the error path. The test also acts as documentation of the partial-write semantics.

---

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Focuses on better patterns, increased coverage, and more stable tests

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Pull request overview

Improves test coverage and documents edge-case behavior for the shared internal/httputil helper that writes JSON HTTP responses.

Changes:

• Adds a new subtest that exercises the json.Marshal error path in WriteJSONResponse.
• Asserts the observable behavior on marshal failure (headers/status written, empty body).

Show a summary per file

File	Description
internal/httputil/httputil_test.go	Adds coverage for the marshal-error branch and documents the “headers committed before marshal” behavior via assertions.

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• Files reviewed: 1/1 changed files
• Comments generated: 1