phase29ap(p4): shrink joinir legacy loop pattern table

docs/development/current/main/10-Now.md

@@ -3,7 +3,7 @@
 ## Current Focus
 
 - Phase: `docs/development/current/main/phases/phase-29ap/README.md`
-- Next: Phase 29ap P4 (planned; see `docs/development/current/main/phases/phase-29ap/README.md`)
+- Next: Phase 29ap P5 (planned; see `docs/development/current/main/phases/phase-29ap/README.md`)
 
 ## Gate (SSOT)
 

docs/development/current/main/30-Backlog.md

@@ -5,7 +5,7 @@ Scope: 「次にやる候補」を短く列挙するメモ。入口は `docs/dev
 
 ## Active
 
-- Phase 29ap: `docs/development/current/main/phases/phase-29ap/README.md` (Next: P4 planned)
+- Phase 29ap: `docs/development/current/main/phases/phase-29ap/README.md` (Next: P5 planned)
 - JoinIR regression gate SSOT: `docs/development/current/main/phases/phase-29ae/README.md`
 - CorePlan hardening (docs-first): `docs/development/current/main/phases/phase-29al/README.md`
 

docs/development/current/main/design/coreplan-migration-roadmap-ssot.md

@@ -34,7 +34,7 @@ Related:
 ## 1.1 Current (active)
 
 - Active phase: `docs/development/current/main/phases/phase-29ap/README.md`
-- Next step: Phase 29ap P4 (planned)
+- Next step: Phase 29ap P5 (planned)
 
 ## 2. すでに固めた SSOT（再発防止の土台）
 

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

@@ -53,7 +53,16 @@ Gate (SSOT):
   - No new logs or error strings.
   - Fallback remains `Ok(None)` when shape does not match.
 
+## P4: JoinIR legacy table shrink (Pattern8 removal) ✅
+
+- Scope:
+  - Remove Pattern8 from `LOOP_PATTERNS` so plan/composer stays SSOT for normal loops.
+  - Keep legacy table as last resort for Pattern2/4/9 only.
+- Guardrails:
+  - No change to logs or error strings.
+  - Legacy routing remains a last-resort fallback.
+
 ## Next (planned)
 
-- P4: Router pattern-name branching reduction (planner outcome + composer SSOT)
-- P5: Facts/Feature expansion if needed
+- P5: Router pattern-name branching reduction (planner outcome + composer SSOT)
+- P6: Facts/Feature expansion if needed

src/mir/builder/control_flow/joinir/patterns/router.rs

@@ -222,7 +222,7 @@ pub(crate) struct LoopPatternEntry {
 ///
 /// **IMPORTANT**: Patterns are tried in array order (SSOT).
 /// Array order defines priority - earlier entries are tried first.
-/// Pattern4 → Pattern8 → Pattern9 → Pattern2
+/// Pattern4 → Pattern9 → Pattern2
 ///
 /// # Current Patterns (Structure-based detection, established Phase 131-11+)
 ///
@@ -243,6 +243,7 @@ pub(crate) struct LoopPatternEntry {
 ///
 /// Note: func_name is now only used for debug logging, not pattern detection
 /// Phase 286: Pattern5 removed (migrated to Plan-based routing)
+/// Phase 29ap P4: Pattern8 removed (migrated to Plan-based routing)
 pub(crate) static LOOP_PATTERNS: &[LoopPatternEntry] = &[
     LoopPatternEntry {
         name: "Pattern6_NestedLoopMinimal",  // Phase 188.3: 1-level nested loop
@@ -258,11 +259,6 @@ pub(crate) static LOOP_PATTERNS: &[LoopPatternEntry] = &[
     // Pattern6_ScanWithInit now handled via extract_scan_with_init_plan() + PlanLowerer
     // Phase 273 P2: Pattern7 entry removed (migrated to Plan-based routing)
     // Pattern7_SplitScan now handled via extract_split_scan_plan() + PlanLowerer
-    LoopPatternEntry {
-        name: "Pattern8_BoolPredicateScan", // Phase 259 P0: boolean predicate scan (is_integer/is_valid)
-        detect: super::pattern8_scan_bool_predicate::can_lower,
-        lower: super::pattern8_scan_bool_predicate::lower,
-    },
     LoopPatternEntry {
         name: "Pattern9_AccumConstLoop", // Phase 270 P1: accumulator const loop (橋渡しパターン, before P1)
         detect: super::pattern9_accum_const_loop::can_lower,
@@ -293,7 +289,7 @@ pub(crate) static LOOP_PATTERNS: &[LoopPatternEntry] = &[
 /// This function implements the following routing strategy:
 /// 1. Try Plan-based Pattern6 (extract_scan_with_init_plan) → DomainPlan
 /// 2. Try Plan-based Pattern7 (extract_split_scan_plan) → DomainPlan
-/// 3. Fall through to legacy Pattern2/4/8/9 table for other patterns
+/// 3. Fall through to legacy Pattern2/4/9 table for other patterns
 ///
 /// The Plan line (Extractor → Normalizer → Verifier → Lowerer) is the
 /// current operational SSOT for Pattern6/7. Legacy patterns (1/2/4/8/9) use
@@ -308,7 +304,7 @@ pub(crate) static LOOP_PATTERNS: &[LoopPatternEntry] = &[
 /// SSOT Entry Points:
 /// - Pattern6: src/mir/builder/control_flow/plan/normalizer.rs (ScanWithInit normalization)
 /// - Pattern7: src/mir/builder/control_flow/plan/normalizer.rs (SplitScan normalization)
-/// - Pattern2/4/8/9: src/mir/builder/control_flow/joinir/patterns/pattern*.rs (direct lowering)
+/// - Pattern2/4/9: src/mir/builder/control_flow/joinir/patterns/pattern*.rs (direct lowering)
 pub(crate) fn route_loop_pattern(
     builder: &mut MirBuilder,
     ctx: &LoopPatternContext,