docs: update Now/INDEX for Phase 129-B join_k as-last

docs/development/current/main/phases/phase-129/README.md

@@ -134,8 +134,8 @@ x=1; flag=1; if flag==1 { x=2 }; print(x); return "OK"
 ## Acceptance Criteria
 
 - ✅ P0: Phase 128 LLVM EXE smoke passes
-- [ ] P1: join_k materialized in builder.rs
-- [ ] P1: verify_normalized_structure enforces join_k properties
+- ✅ P1-B: join_k materialized for if-as-last (then/else tail-call join_k)
+- ✅ P1-B: verify_normalized_structure enforces join_k tailcall + PHI禁止
 - [ ] P2: Phase 129 fixture + VM smoke passes
 - [ ] P3: Documentation updated
 - [ ] Regression: phase103, phase118, phase128 all PASS