refactor(joinir): boxify Pattern2 routing and schedule facts

src/mir/builder/control_flow/joinir/patterns/policies/README.md

@@ -55,6 +55,23 @@
 
 ---
 
+### loop_true_read_digits_policy.rs (Phase 104/105)
+**現在の場所**: `patterns/policies/loop_true_read_digits_policy.rs`
+
+**責務**: `loop(true)` + break-only digits（`read_digits_from` family）の認識とルーティング
+
+**判断基準**:
+- `loop(true)` である
+- read-digits(loop(true)) detector に一致する
+- `ReadDigitsBreakConditionBox` が eos 条件 + digit 条件を抽出できる
+
+**出力**:
+- `PolicyDecision::Use(LoopTrueReadDigitsPolicyResult)` - `break_when_true := (ch == \"\") || !(digit_cond)` と `ch` allow-list
+- `PolicyDecision::Reject(String)` - 検出失敗理由（Fail-Fast）
+- `PolicyDecision::None` - 該当なし
+
+---
+
 ### body_local_policy.rs
 **現在の場所**: `patterns/body_local_policy.rs`
 

src/mir/builder/control_flow/joinir/patterns/policies/loop_true_read_digits_policy.rs

@@ -0,0 +1,61 @@
+//! loop(true) + break-only digits (read_digits_from family) policy
+//!
+//! Goal: keep Pattern2 core lowering structural by moving shape recognition + routing
+//! for loop(true) read-digits family into a dedicated policy box.
+//!
+//! This policy is intentionally narrow:
+//! - It only triggers when the body matches the read-digits(loop(true)) detector.
+//! - It returns a normalized "break when true" condition AST:
+//!     `break_when_true := (ch == "") || !(digit_cond)`
+//! - It provides the single allowed body-local variable name (`ch`) for condition lowering.
+
+use super::PolicyDecision;
+use crate::ast::{ASTNode, BinaryOperator, Span, UnaryOperator};
+
+pub(crate) struct LoopTrueReadDigitsPolicyResult {
+    pub break_condition_node: ASTNode,
+    pub allowed_ch_var: String,
+}
+
+pub(crate) fn classify_loop_true_read_digits(
+    condition: &ASTNode,
+    body: &[ASTNode],
+) -> PolicyDecision<LoopTrueReadDigitsPolicyResult> {
+    use crate::mir::builder::control_flow::joinir::patterns::{
+        ast_feature_extractor::detect_read_digits_loop_true_pattern,
+        loop_true_counter_extractor::LoopTrueCounterExtractorBox,
+        read_digits_break_condition_box::ReadDigitsBreakConditionBox,
+    };
+
+    if !LoopTrueCounterExtractorBox::is_loop_true(condition) {
+        return PolicyDecision::None;
+    }
+    if detect_read_digits_loop_true_pattern(body).is_none() {
+        return PolicyDecision::None;
+    }
+
+    let (ch_var, eos_cond, digit_cond) =
+        match ReadDigitsBreakConditionBox::extract_eos_and_digit_condition(body) {
+            Ok(v) => v,
+            Err(e) => return PolicyDecision::Reject(e),
+        };
+
+    let break_on_not_digit = ASTNode::UnaryOp {
+        operator: UnaryOperator::Not,
+        operand: Box::new(digit_cond),
+        span: Span::unknown(),
+    };
+
+    let break_when_true = ASTNode::BinaryOp {
+        operator: BinaryOperator::Or,
+        left: Box::new(eos_cond),
+        right: Box::new(break_on_not_digit),
+        span: Span::unknown(),
+    };
+
+    PolicyDecision::Use(LoopTrueReadDigitsPolicyResult {
+        break_condition_node: break_when_true,
+        allowed_ch_var: ch_var,
+    })
+}
+

src/mir/builder/control_flow/joinir/patterns/policies/mod.rs

@@ -32,3 +32,4 @@ pub enum PolicyDecision<T> {
 
 pub(in crate::mir::builder) mod p5b_escape_derived_policy;
 pub(in crate::mir::builder) mod trim_policy;
+pub(in crate::mir::builder) mod loop_true_read_digits_policy;