fix: return Catalyst HTTP exception responses from MockHTTP tests #1652

Parent: #1117. The HTTP::Message and LWP suites pass after PR #1641, but Catalyst Runtime 5.90132's HTTP exception acceptance path still fails on PerlOnJava.

What was done and why it was not enough

PR #1641 fixed the confirmed HTTP::Message-adjacent bzip2 output limit and interpreter zlib constant import defects and added focused unit tests. The unchanged HTTP::Message and LWP suites now pass. That coverage does not exercise Catalyst's HTTP exception responses, which travel through a PSGI response callback and then HTTP::Response->from_psgi.

Reproduction

Run t/http_exceptions_backcompat.t or t/http_exceptions.t from the Catalyst-Runtime 5.90132 distribution with the JVM backend. Both reach Plack::Test::MockHTTP::request and die with:

Can't call method "request" on an undefined value at Plack/Test/MockHTTP.pm line 29

t/http_exceptions_backcompat.t completes two assertions before aborting. t/http_exceptions.t completes 11 of its planned 17 assertions before aborting. System Perl passes both files (29 tests total) with the same installed prerequisites.

Root cause and proposed fix

The Catalyst PSGI app's HTTP-exception response reaches Plack::Test::MockHTTP::request line 24, which passes it to HTTP::Response->from_psgi. The conversion returns undef, then line 29 dereferences it. In HTTP::Message::PSGI::res_from_psgi, the CODE response branch records $res only when the responder callback runs; it returns $res immediately after invoking the PSGI callback. If Catalyst supplies a delayed/streaming responder form, that callback has not populated $res yet. Trace the exact response shape from Catalyst, then make the PerlOnJava path complete the response conversion for that supported PSGI form (or report unsupported asynchronous responses explicitly instead of returning undef).

Acceptance criteria

• Confirm the exact PSGI response shape from the failing Catalyst exception action and compare it with system Perl.
• Fix response conversion so it returns a valid HTTP::Response for the supported response form and preserves callback/body semantics.
• Pass both tests on JVM and interpreter, including all 17 planned assertions in t/http_exceptions.t.
• Rerun the Catalyst HTTP consumer selection required by Restore HTTP::Message 7.04 compatibility #1117.