fix: use tabs for Go indentation and column-align struct fields

gofmt requires tab indentation (not spaces) and column-aligns struct
field declarations and composite literal keys. Updated the Go codegen
to emit tabs for all indentation and compute proper padding for field
alignment in wrapper structs and constructors.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: stephentoub