fix(normalization): Phase 143 execution fix - Param region SSOT

Problem: normalized_helpers allocated env params as ValueId(1,2...)
in PHI Reserved region (0-99) instead of Param region (100-999)
per JoinValueSpace contract.

Root cause: All 4 normalized shadow modules started from
next_value_id=1, violating the Param region contract.

Solution:
- Add NormalizedHelperBox::alloc_env_params_param_region()
  that allocates params starting from PARAM_MIN (100)
- Update 4 normalized shadow files to use new API:
  - loop_true_if_break_continue.rs
  - loop_true_break_once.rs
  - if_as_last_join_k.rs
  - post_if_post_k.rs
- Fix instruction_rewriter.rs type mismatch
  (func.signature.params → func.params)

Verification:
- Unit tests: 69/69 PASS
- VM smoke: exit code 7 ✅
- LLVM EXE smoke: exit code 7 ✅ (timeout resolved!)

ValueId Space Contract (Phase 201):
| Region       | Range    | Purpose                      |
|--------------|----------|------------------------------|
| PHI Reserved | 0-99     | Loop header PHI dst          |
| Param        | 100-999  | env params (flag, counter)   |
| Local        | 1000+    | Const, BinOp, condition      |

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

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

@@ -992,11 +992,18 @@ pub(super) fn merge_and_rewrite(
     if let Some(boundary) = boundary {
         use crate::mir::builder::joinir_inline_boundary_injector::BoundaryInjector;
 
-        // Get entry function's entry block (first function by convention)
+        // Get entry function's entry block.
+        //
+        // Phase 143 fix: Normalized shadow fragments emit multiple helper functions
+        // (e.g. condition_fn) whose names may sort before the true entry.
+        // Choosing `.iter().next()` can therefore pick the wrong function and skip
+        // host→JoinIR Copy injection. Instead, pick the function whose params match
+        // the boundary.join_inputs (the entry env params).
         let (entry_func_name, entry_func) = mir_module
             .functions
             .iter()
-            .next()
+            .find(|(_, func)| func.params == boundary.join_inputs)
+            .or_else(|| mir_module.functions.iter().next())
             .ok_or("JoinIR module has no functions")?;
         let entry_block_remapped = remapper
             .get_block(entry_func_name, entry_func.entry_block)