Fix race condition in shelley manual update path causing binary removal

[exedev-shelley]

Author: eightsixfivezero
Channel: #shelley
Link: https://discord.com/channels/1405685085923049482/1450334528210993295/1526379611859058849

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Description

There is a race condition in the shelley manual update path that can be triggered by two upgrade requests in quick succession. This race condition causes the shelley binary to be completely removed.

Impact

• Two rapid upgrade requests can result in loss of the shelley binary
• This makes the system unusable until the binary is restored

Next Steps

• Investigate the manual update path implementation
• Identify the exact point where concurrent upgrade requests cause the binary deletion
• Implement proper synchronization/locking to prevent concurrent upgrades
• Add tests to verify the fix handles rapid successive upgrade requests