chore: update go-flashduty SDK

[ysyneu]

Summary

• bump go-flashduty to v0.5.4-0.20260626064127-3f90f8e0e38b, which includes the merged public OpenAPI refresh
• regenerate CLI commands and Flashduty skill command cards from the updated SDK/OpenAPI surface
• align cligen method-name stripping with the SDK generator so generated commands keep resolving stable SDK method names
• update the local golangci-lint pin to support the repo's Go 1.25.1 module and serialize lint runners

Validation

• make
• go run ./internal/cmd/skilldoc check