CVE-2026-111951: curl -OJ truncate without filename

Summary: With `-O -J`, when a response carries a `Content-Disposition` header without a usable `filename=` (for example `inline`) before the one that names an existing file, curl truncates that existing file to 0 bytes and then exits 23 saying it refused to overwrite it. This breaks the promise in …

HTTP/1.1 200 OK
Content-Disposition: inline
Content-Disposition: attachment; filename="victim"
Content-Length: 8

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