Background

V3MutationService.kt and V3CompatibleTableBinding.kt contain 95%+ identical code between mutateEdge and mutateMultiEdge methods. This duplication has already caused a bug: mutateMultiEdge is missing LockAcquisitionFailedException error handling that mutateEdge has — errors propagate and fail the entire request instead of returning ERROR status and clearing stale locks.

Task

• V3CompatibleTableBinding: Extract buildHBaseMutations() private helper (100% identical HBase mutation construction: Put, Increment, Delete)
• V3CompatibleTableBinding: Extract decodeCurrentState() private helper (identical state decoding logic)
• V3MutationService: Extract resolveMutationContext() helper (label validation + context initialization)
• V3MutationService: Extract writeCdc() helper (CDC message creation + publish)
• V3MutationService: Extract handleMutationError() helper and apply to both methods
• Bug fix: Add onErrorResume for LockAcquisitionFailedException to mutateMultiEdge

Done When

• All existing tests pass (./gradlew :engine:test, ./gradlew :server:test)
• No changes to public API signatures (controller compatibility preserved)
• No changes to core module types
• mutateMultiEdge handles LockAcquisitionFailedException identically to mutateEdge

Notes

• Minimal extraction approach — small helper functions, no heavyweight generics or sealed interfaces
• Expected reduction: V3CompatibleTableBinding ~65 lines, V3MutationService ~50 lines
• Key difference between Edge/MultiEdge: Pair<Any, Any> (source, target) vs single Any (id) key

Created by claude code (opus 4.6)