0355 — CLI flags map onto the sparse config structs via cmd.Flags().Changed

Context. AlterConfig distinguishes nil (leave alone) from an explicit zero value, but a flag’s value alone cannot make that distinction — an unset bool flag and --flag=false read identically. Dated approximately; built across July 2026.

Decision. Flags map 1:1 onto the config structs, and only flags the operator actually passed — detected with cmd.Flags().Changed — become non-nil fields. Bools included: --flag=false is a real set, distinct from not passing the flag.

Consequences. The nil / explicit-zero tri-state survives end to end from the command line to the COALESCE UPDATE, so vulkan topic alter can set a field to its zero value or leave it alone, never confusing the two. alter renders an OLD → NEW diff table so the operator sees exactly which fields will change.