fix(http): prevent connection reuse when --fail skips response body (test 1328)

[jonwiggins]

Summary

• When --fail triggers on a 4xx response with URL globbing, the body read is skipped but the connection was returned to the pool with unread body data still on the socket
• The next URL's request would reuse that connection and read stale body data instead of fresh response headers, causing a hang
• Fix: check fail_skip && has_body_framing (Content-Length or chunked) in the can_reuse calculation to prevent reusing connections with undrained body data

Closes #122

Test plan

• Added unit test request_fail_on_error_no_reuse_with_body verifying can_reuse = false when --fail skips a 404 response with Content-Length
• All existing tests pass (no regressions)
• cargo clippy and cargo fmt pass
• curl test 1328 should pass (requires curl test infrastructure)

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