dracon-sync v0.113.6 — 2026-07-28

Completes v0.113.5: M4 trailing-drain unification via shared
apply_outcome function + ApplyOutcome enum (both call sites use
the same path; pre-fix divergence structurally impossible).

Repos promoted to pub(crate); helper extracted for testability.
Regression test test_m4_helper_structurally_unified drives each
SyncOutcome variant through the helper.

Test posture: 852 passed (was 837 before v0.113.5), 3 ignored.
cargo clippy ... -- -D warnings clean.
cargo build --release --locked clean.

See release-notes-v0.113.6.md for full notes.