Add core type definitions and constants for the command zone feature:
- zone_names.h: Add command zone name constants (command, partner,
companion, background) for protocol and lookup operations
- command_zone_types.h: Define CommandZoneType enum, ZoneVisibility enum,
and StateChangeResult struct for state machine logic
- counter_ids.h: Define shared counter IDs and names for commander tax
tracking (IDs 8-9 reserved to avoid conflicts with user counters)
These headers are intentionally minimal and dependency-free to enable
inclusion in both production code and isolated unit tests.
