fix(joinir): Phase 170-B Break condition delegation to condition_to_joinir

Remove hardcoded break condition (i >= 2) from loop_with_break_minimal.rs.
Now delegates to condition_to_joinir for dynamic break condition lowering.

Changes:
- Add extract_break_condition() to ast_feature_extractor.rs
- Pattern2 lowerer extracts break condition AST and passes to lowerer
- loop_with_break_minimal.rs uses BoolExprLowerer instead of hardcoded values
- Add TrimTest.main/0 to JoinIR routing whitelist

Box Theory compliance:
- Single responsibility: Pattern2 handles structure, condition_to_joinir handles lowering
- Zero hardcoding: All break conditions now dynamic

Verified:
- test_loop_return.hako (i >= 2) → RC: 2 ✅
- test_trim_loop.hako (i >= 3) → RC: 3 ✅

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

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

@@ -201,6 +201,45 @@ fn has_break_node(node: &ASTNode) -> bool {
     }
 }
 
+/// Phase 170-B: Extract break condition from loop body
+///
+/// Searches for the first `if <condition> { break }` pattern in the loop body.
+/// This is used to delegate break condition lowering to `condition_to_joinir`.
+///
+/// # Arguments
+///
+/// * `body` - Loop body statements to search
+///
+/// # Returns
+///
+/// `Some(&ASTNode)` - The condition AST node from `if <condition> { break }`
+/// `None` - No break statement found or break is not in a simple if statement
+///
+/// # Example
+///
+/// ```nyash
+/// loop(i < 3) {
+///   if i >= 2 { break }  // <- Returns the "i >= 2" condition
+///   i = i + 1
+/// }
+/// ```
+pub fn extract_break_condition(body: &[ASTNode]) -> Option<&ASTNode> {
+    for stmt in body {
+        if let ASTNode::If {
+            condition,
+            then_body,
+            ..
+        } = stmt
+        {
+            // Check if the then_body contains a break statement
+            if then_body.iter().any(|node| matches!(node, ASTNode::Break { .. })) {
+                return Some(condition.as_ref());
+            }
+        }
+    }
+    None
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs

@@ -141,9 +141,14 @@ impl MirBuilder {
             variable_definitions: BTreeMap::new(),
         };
 
-        // Phase 169 / Phase 171-fix / Phase 172-3: Call Pattern 2 lowerer with ConditionEnv
+        // Phase 170-B: Extract break condition from loop body
+        use super::ast_feature_extractor;
+        let break_condition = ast_feature_extractor::extract_break_condition(_body)
+            .ok_or_else(|| "[cf_loop/pattern2] Failed to extract break condition from loop body".to_string())?;
+
+        // Phase 169 / Phase 171-fix / Phase 172-3 / Phase 170-B: Call Pattern 2 lowerer with break_condition
         // Phase 33-14: Now returns (JoinModule, JoinFragmentMeta) for expr_result + carrier separation
-        let (join_module, fragment_meta) = match lower_loop_with_break_minimal(scope, condition, &env, &loop_var_name) {
+        let (join_module, fragment_meta) = match lower_loop_with_break_minimal(scope, condition, break_condition, &env, &loop_var_name) {
             Ok((module, meta)) => (module, meta),
             Err(e) => {
                 // Phase 195: Use unified trace

src/mir/builder/control_flow/joinir/routing.rs

@@ -76,6 +76,7 @@ impl MirBuilder {
             "TrimTest.trim/1" => true,
             "Main.trim/1" => true,  // Phase 171-fix: Main box variant
             "Main.trim_string_simple/1" => true,  // Phase 33-13: Simple trim variant
+            "TrimTest.main/0" => true,  // Phase 170: TrimTest.main for loop pattern test
             _ => false,
         };