F412 production and verification contract

Producer
- compiler/ContinuationLowering.cpp
- LoopMemoryPhiByteLaneCertificate::isStrided
- loopMemoryPhiByteLaneInitialization
- loopMemoryPhiByteLaneRecord
- bounded-strided-loop-memoryphi-byte-lane-induction
- symcc-loop-memoryphi-byte-lane-induction-v2

Consumer and runtime
- util/live_continuation.py
- LiveContinuationExecutor._loop_memoryphi_byte_lane_initialization
- exact base/extension capability closure
- scalar PHI edge-copy and latch-step replay
- pointer_offset base/index/scale/ordering replay
- complete aliases versus recurrence-reachable writer subset
- unique writer byte owner and load-lane Cartesian product
- bound capacity and whole-domain no-wrap proof
- path-local byte-init authority

Production fixtures and checkers
- test/live_strided_loop_memoryphi_byte_lane_induction.ll
- util/check_live_continuation_lowering.py
- benchmark/generate_strided_loop_memoryphi_byte_lane_fixture.py

Independent semantics and mechanism cost
- benchmark/check_strided_loop_memoryphi_byte_lane_oracles.py
- benchmark/benchmark_strided_loop_memoryphi_byte_lane.py
- test/test_strided_loop_memoryphi_byte_lane_induction.py

Documentation and diagram
- docs/codex/research-progress/Strided_Loop_MemoryPhi_Residue_Cover_F412_2026-08-16.md
- docs/codex/diagrams/strided-loop-memoryphi-residue-cover-f412.svg
- docs/codex/diagrams/strided-loop-memoryphi-residue-cover-f412.png