fix: upgrade to Go 1.25

[google-labs-jules]

Upgrade project to Go 1.25.0

• Update go.mod to specify go 1.25.0.
• Update godebug default=go1.25 in go.mod.
• Run go mod tidy to update dependencies.
• Verified with make test using Go 1.25.5.

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PR created automatically by Jules for task 14515963442546575644 started by @josmo

[google-labs-jules]

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