Fix S1001 linter warning: use copy() instead of manual loop

[rubensantoniorosa2704]

Replaces a manual slice copy loop with Go's built-in copy() function to fix the staticcheck S1001 linter warning.

Before:

fields := make([]Field, len(s.Fields))
for i, f := range s.Fields {
    fields[i] = f
}

After:

fields := make([]Field, len(s.Fields))
copy(fields, s.Fields)

Why:

• Idiomatic Go code
• Fixes linter warning: "should use copy(to, from) instead of a loop"
• No functional changes, just optimization