🔐 Replace shell-string execution with safer command wrappers

[fusion94]

Summary

Replace shell-string execution patterns in command-center with safer command wrappers.

Why

The app currently shells out with interpolated command strings for operations like gh calls. This is convenient, but over time it increases risk and makes behavior harder to validate.

Proposed scope

• move from broad shell-string execution toward safer argument-based wrappers where possible
• isolate command execution in a small utility layer
• keep existing behavior while reducing risk

Acceptance criteria

• command execution is centralized
• shell interpolation is reduced or eliminated for key operations
• GitHub actions like issue closing still work after the refactor