Summary

Normalize container_system common_system integration gates to KCENON_HAS_COMMON_SYSTEM.

5W1H Specification

• Who: container_system maintainers
• What: Replace CONTAINER_USE_COMMON_SYSTEM and BUILD_WITH_COMMON_SYSTEM checks
• Where: container core headers/sources
• When: TBD
• Why: Remove naming fragmentation and duplicated checks
• How: Include feature_flags header and switch macros

Parent Issue

kcenon/common_system#223

Tasks

• Include feature_flags.h in container core
• Replace CONTAINER_USE_COMMON_SYSTEM and BUILD_WITH_COMMON_SYSTEM checks
• Update docs to reference KCENON_HAS_COMMON_SYSTEM

Acceptance Criteria

• No CONTAINER_USE_COMMON_SYSTEM checks remain
• Common_system integration behavior is unchanged