API mock interceptor: XHR header case sensitivity in request matching

[tyevco]

Summary

The API mock interceptor stores XHR request headers with their original case but the matcher attempts case-insensitive lookup with an incomplete fallback.

Current Behavior

In interceptor.ts (line 205):

request.headers[name] = value;  // stores with original case, e.g. "Content-Type"

In matcher.ts (line 37):

const requestHeaderValue = request.headers[key.toLowerCase()] || request.headers[key];

This fallback only works when the mock rule's header name matches either the lowercased or exact-case version of the stored header. It fails when the cases don't align in either direction.

Example Failure

Mock rule: { headers: { "content-type": "application/json" } }
Stored header: request.headers["Content-Type"] = "application/json"

Lookup:

• request.headers["content-type"] → undefined (stored as Content-Type)
• request.headers["content-type"] → undefined (same key, same result)

The header match fails even though semantically it should match.

Suggested Fix

Normalize headers to lowercase on storage:

request.headers[name.toLowerCase()] = value;

Or use a case-insensitive lookup helper in the matcher.

Priority

Low — most XHR libraries use standard casing (Content-Type, Authorization) which would match the typical mock rule casing.