feat(joinir): Phase 77 - BindingId expansion implementation (dev-only)

Phase 77 implements promoted_bindings population in DigitPos/Trim promoters
and deprecates legacy name-based resolution paths.

Changes:
- DigitPosPromoter: Added binding_map field and record_promoted_binding() calls
- TrimLoopHelper: Added binding_map field for ch → is_ch_match tracking
- Pattern2/4: Wired binding_map from builder.binding_map to promoters
- Legacy deprecation: Added #[deprecated] to resolve_promoted_join_id()
- Dual-path design: BindingId priority + name fallback maintained

Files modified (8):
- pattern2_with_break.rs, pattern4_with_continue.rs: binding_map wiring
- trim_loop_lowering.rs: Trim promoter integration
- carrier_info.rs: Deprecation warnings
- scope_manager.rs: Deprecated fallback paths
- loop_body_carrier_promoter.rs: Trim binding_map support
- loop_body_cond_promoter.rs: Orchestrator updates
- loop_body_digitpos_promoter.rs: DigitPos binding_map support

Tests: 958/958 PASS (zero regressions)
Design: Type-safe BindingId mapping replaces string-based promoted variable resolution

Phase 78+ will delete deprecated code (~50 lines) and make binding_map required.

🤖 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/patterns/pattern2_with_break.rs

@@ -250,6 +250,8 @@ fn promote_and_prepare_carriers(
             break_cond: Some(&inputs.break_condition_node),
             continue_cond: None,
             loop_body: body,
+            #[cfg(feature = "normalized_dev")]
+            binding_map: Some(&builder.binding_map),
         };
 
         match LoopBodyCondPromoter::try_promote_for_condition(promotion_req) {

src/mir/builder/control_flow/joinir/patterns/pattern4_with_continue.rs

@@ -239,6 +239,8 @@ fn prepare_pattern4_context(
             break_cond: None, // Pattern 4 has no break
             continue_cond,
             loop_body: &normalized_body,
+            #[cfg(feature = "normalized_dev")]
+            binding_map: Some(&builder.binding_map),
         };
 
         match LoopBodyCondPromoter::try_promote_for_condition(promotion_req) {

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

@@ -226,6 +226,8 @@ impl TrimLoopLowerer {
             cond_scope: &cond_scope,
             break_cond: Some(break_cond),
             loop_body: body,
+            #[cfg(feature = "normalized_dev")]
+            binding_map: Some(&builder.binding_map),
         };
 
         match LoopBodyCarrierPromoter::try_promote(&request) {
@@ -236,6 +238,9 @@ impl TrimLoopLowerer {
                 );
 
                 // Step 3: Convert to CarrierInfo and merge
+                #[cfg(feature = "normalized_dev")]
+                let promoted_carrier = trim_info.to_carrier_info(Some(&builder.binding_map));
+                #[cfg(not(feature = "normalized_dev"))]
                 let promoted_carrier = trim_info.to_carrier_info();
                 carrier_info.merge_from(&promoted_carrier);