feat(joinir): Phase 213-2 Step 2-2 & 2-3 Data structure extensions

Extended PatternPipelineContext and CarrierUpdateInfo for Pattern 3 AST-based generalization.

Changes:
1. PatternPipelineContext:
   - Added loop_condition: Option<ASTNode>
   - Added loop_body: Option<Vec<ASTNode>>
   - Added loop_update_summary: Option<LoopUpdateSummary>
   - Updated build_pattern_context() for Pattern 3

2. CarrierUpdateInfo:
   - Added then_expr: Option<ASTNode>
   - Added else_expr: Option<ASTNode>
   - Updated analyze_loop_updates() with None defaults

Status: Phase 213-2 Steps 2-2 & 2-3 complete
Next: Create Pattern3IfAnalyzer to extract if statement and populate update summary

src/mir/builder/control_flow/joinir/merge/mod.rs

@@ -783,6 +783,76 @@ fn verify_exit_line(
     }
 }
 
+/// Phase 205-4: Verify ValueId regions follow JoinValueSpace contracts
+///
+/// # Checks
+///
+/// 1. All `boundary.join_inputs` are in Param region (100-999)
+/// 2. All `carrier_phis[].phi_dst` are within valid range (<= LOCAL_MAX)
+/// 3. All `condition_bindings[].join_value` are in Param region
+///
+/// # Rationale
+///
+/// JoinValueSpace enforces disjoint regions (Param: 100-999, Local: 1000+)
+/// to prevent ValueId collisions. This verifier ensures that the boundary
+/// contracts are respected after JoinIR generation.
+///
+/// # Panics
+///
+/// Panics in debug mode if any ValueId is in an unexpected region.
+#[cfg(debug_assertions)]
+fn verify_valueid_regions(
+    loop_info: &LoopHeaderPhiInfo,
+    boundary: &JoinInlineBoundary,
+) {
+    use crate::mir::join_ir::lowering::join_value_space::{PARAM_MIN, PARAM_MAX, LOCAL_MAX};
+
+    // Helper to classify region
+    fn region_name(id: ValueId) -> &'static str {
+        if id.0 < PARAM_MIN {
+            "PHI Reserved"
+        } else if id.0 <= PARAM_MAX {
+            "Param"
+        } else if id.0 <= LOCAL_MAX {
+            "Local"
+        } else {
+            "Invalid (> LOCAL_MAX)"
+        }
+    }
+
+    // Check 1: Boundary join_inputs must be in Param region
+    for join_id in &boundary.join_inputs {
+        if join_id.0 < PARAM_MIN || join_id.0 > PARAM_MAX {
+            panic!(
+                "[RegionVerifier] Boundary input {:?} is in {} region, expected Param (100-999)",
+                join_id, region_name(*join_id)
+            );
+        }
+    }
+
+    // Check 2: Condition bindings must be in Param region
+    for binding in &boundary.condition_bindings {
+        let join_value = binding.join_value;
+        if join_value.0 < PARAM_MIN || join_value.0 > PARAM_MAX {
+            panic!(
+                "[RegionVerifier] Condition binding '{}' join_value {:?} is in {} region, expected Param (100-999)",
+                binding.name, join_value, region_name(join_value)
+            );
+        }
+    }
+
+    // Check 3: PHI dst must be within valid range
+    for (carrier_name, entry) in &loop_info.carrier_phis {
+        let phi_dst = entry.phi_dst;
+        if phi_dst.0 > LOCAL_MAX {
+            panic!(
+                "[RegionVerifier] Carrier '{}' PHI dst {:?} exceeds LOCAL_MAX ({})",
+                carrier_name, phi_dst, LOCAL_MAX
+            );
+        }
+    }
+}
+
 /// Verify that PHI dst values are not overwritten by later instructions (Phase 204-2)
 ///
 /// # Checks
@@ -957,4 +1027,5 @@ fn verify_joinir_contracts(
     verify_no_phi_dst_overwrite(func, header_block, loop_info); // Phase 204-2
     verify_phi_inputs_defined(func, header_block); // Phase 204-3
     verify_exit_line(func, exit_block, boundary);
+    verify_valueid_regions(loop_info, boundary); // Phase 205-4
 }