docs: closeout phase29af; start phase29ag

docs/development/current/main/phases/phase-29ag/README.md

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+# Phase 29ag: JoinIR merge SSOT unification (post-29af)
+
+Goal: Phase 29af で固めた boundary/layout/contract を前提に、merge 内の order SSOT をさらに一箇所へ寄せて回帰余地を減らす（仕様不変）。
+
+## Why now
+
+- Phase 29af で carrier order SSOT（`BoundaryCarrierLayout`）と整合契約（P4）まで揃った
+- 次は “同じ order を別ソースで再計算する箇所” を減らし、未来の refactor でズレない構造にする
+
+## P0: Coordinator param remap uses BoundaryCarrierLayout
+
+- 指示書: `docs/development/current/main/phases/phase-29ag/P0-COORDINATOR-USES-BOUNDARY-CARRIER-LAYOUT-INSTRUCTIONS.md`
+
+## Verification (SSOT)
+
+- `cargo build --release`
+- `./tools/smokes/v2/run.sh --profile quick`
+- `./tools/smokes/v2/profiles/integration/joinir/phase29ae_regression_pack_vm.sh`