Add config accessor functions for sync mode, conflict strategy, and
federation sovereignty tier settings. These functions:
- Read from config.yaml via viper
- Validate against known valid values
- Return sensible defaults when not set
- Log warnings to stderr when invalid values are configured (instead
of silently falling back to defaults)
Closes: hq-ew1mbr.26
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
e82e15a8c2