Clarify empty response body behavior in parse tests

[yesudeep]

Summary

There are TODOs in the parse tests questioning whether the current behavior for empty response bodies is correct. This needs investigation and documentation.

Locations

• js/src/parse.test.ts:859: // TODO: Check whether this is the correct behavior.
• python/dotpromptz/tests/dotpromptz/parse_test.py:728: # TODO: Check whether this is the correct behavior.
• go/dotprompt/parse_test.go:423: // TODO: May be change this behavior to return a matching body when

Acceptance Criteria

• Review current behavior for empty response bodies
• Document expected behavior in spec
• Update tests with clear assertions or fix implementation