fix(translation): wire v2 tests into CI and clear the code-quality gate

The new tests/test_litellm/translation suite was in no CI shard, so it never
ran and codecov reported 0% patch coverage; add it to the misc unit-test
workflow and the Makefile group so it runs and reports

Allowlist the boundary JSON walkers freeze and thaw in recursive_detector, the
same treatment every other cycle-free JSON/schema walker gets (bounded by input
nesting depth, no cycles possible in JSON)

Drop the unused engine/http.py I/O port; it had no caller in a request-only
slice, so it was dead code with zero coverage. The injected port returns with
the response and stream increment that actually performs I/O

Add failures-as-values tests covering the parser's error branches (malformed
roles, content parts, images, tools, tool_calls, tool_choice) and four more
differential parity cases: system as array, stop as string,
max_completion_tokens, and a tool without a description

.github/workflows/test-unit-misc.yml

@@ -34,6 +34,7 @@ jobs:
         tests/test_litellm/interactions
         tests/test_litellm/passthrough
         tests/test_litellm/vector_stores
+        tests/test_litellm/translation
         tests/test_litellm/test_*.py
       workers: 2
       reruns: 2