docs(phase29ab): closeout P1-P9

docs/development/current/main/design/edgecfg-fragments.md

@@ -361,6 +361,13 @@ MIR Terminator Instructions
 - loop の EdgeCFG 化は、まず **BasicBlockId 層で持っている箇所（Phase 268 の if_form のような場所）**から適用を進める。
 - JoinIR 側の loop は Phase 270 で **fixture/smoke による SSOT 固定**を先に行い、壊れたら最小差分で直す。
 
+## compose SSOT（使い分けガイド）
+
+- `compose::if_`: then/else が **Normal exit** で step/merge に合流する形（Pattern7 split scan の if/else）
+- `compose::cleanup`: main frag に cleanup frag（Return/Normal）を合成して早期離脱を明示する形（Pattern6 scan-with-init）
+- どちらも **Frag の validity を前提** にし、Normalizer が入口で妥当性を保証する
+- Pattern6/7 contract SSOT: `docs/development/current/main/design/pattern6-7-contracts.md`
+
 補足（Phase 270）:
 - Pattern1（simple_while_minimal）は test-only stub のため、一般ループの “基準” には使えない。
 - Phase 270 では “最小の固定形” を Pattern9（AccumConstLoop）として追加し、後で Frag 合成側へ吸収される前提で橋渡しにする。

docs/development/current/main/design/pattern6-7-contracts.md

@@ -0,0 +1,39 @@
+# Pattern6/7 Contracts (SSOT)
+
+This document defines the **contract boundary** for Pattern6/7 extractors.
+It is the SSOT for `NotApplicable` vs `Freeze` decisions.
+
+## Common Rule
+
+- **NotApplicable**: shape mismatch (another pattern may apply)
+- **Freeze**: shape matches but contract is violated (fail-fast)
+
+Tags:
+- Pattern6: `[joinir/phase29ab/pattern6/contract]`
+- Pattern7: `[joinir/phase29ab/pattern7/contract]`
+
+## Pattern6 (ScanWithInit / MatchScan)
+
+Accepted shape:
+- `loop(i < s.length())` or `loop(i <= s.length() - needle.length())`
+- `if s.substring(i, i + 1) == needle { return i }`
+- step update exists and matches direction
+
+Freeze conditions:
+- step update missing
+- forward scan with step != `i = i + 1`
+- reverse scan with step != `i = i - 1`
+Note:
+- plan line is forward-only; reverse scans are currently treated as NotApplicable
+
+## Pattern7 (SplitScan)
+
+Accepted shape:
+- `loop(i <= s.length() - separator.length())`
+- `if s.substring(i, i + separator.length()) == separator`
+- then: `result.push(...)`, `start = i + separator.length()`, `i = start`
+- else: `i = i + 1`
+
+Freeze conditions:
+- then/else update contracts broken (start/i updates)
+- separator literal length != 1 (P0 scope)