Summary

Normalize database_system common_system integration gates to KCENON_HAS_*.

5W1H Specification

• Who: database_system maintainers
• What: Replace BUILD_WITH_COMMON_SYSTEM checks in adapters
• Where: integrated adapters and DI registration
• When: TBD
• Why: Standardize integration detection
• How: Include feature_flags header and update macros

Parent Issue

kcenon/common_system#223

Tasks

• Include feature_flags.h in adapters
• Replace BUILD_WITH_COMMON_SYSTEM (and related integration flags) with KCENON_HAS_*
• Update docs to reference KCENON_* macros

Acceptance Criteria

• Integration checks use KCENON_HAS_*
• Behavior remains unchanged under current build options