Fix Windows release PDB staging

[shijie-oai]

Summary

• Teach the Windows release prebuild staging step to locate Rust/MSVC PDBs emitted with crate-style underscore names.
• Stage PDBs under the shipped hyphenated binary names so the downstream symbol archive step keeps the same artifact contract.
• Keep a fallback for already-hyphenated PDB names and fail with a clear diagnostic if neither form exists.

Root cause

The recent symbol publishing change in #25649 started copying ${binary}.pdb from target/<triple>/release during Windows prebuild staging. Cargo still emits the .exe with the hyphenated binary name, but MSVC PDBs for hyphenated Rust crates are emitted with underscores, for example codex_app_server.pdb for codex-app-server.exe. The release workflow was still building into the expected directory; the new PDB copy step was looking for the wrong filename.

Impact

This unblocks the rust-release Windows prebuilt-binary jobs for hyphenated binaries while preserving the hyphenated PDB names consumed by the final Windows release packaging and symbol archive steps.

Validation

• just fmt from codex-rs
• git diff --check -- .github/workflows/rust-release-windows.yml
• Parsed .github/workflows/rust-release-windows.yml as YAML locally
• Local bash staging sanity test for both underscore-emitted and hyphenated PDB filenames