feat(joinir): Phase 76 - promoted_bindings map (dev-only)

Phase 76 introduces type-safe promotion tracking via promoted_bindings
(BindingId→BindingId map). Replaces fragile string matching hacks with
compiler-checked identity mapping.

Changes:
- carrier_info.rs: Added promoted_bindings field and resolution methods
- pattern4_carrier_analyzer.rs: Updated for BindingId integration
- pattern_pipeline.rs: Carrier resolution via promoted_bindings
- loop_with_break_minimal/tests.rs: Added promoted_bindings tests
- normalized/fixtures.rs: Extended with Phase 76 fixtures

Tests: 5/5 new unit tests PASS (record/resolve/merge/default/overwrite)
Tests: lib 958/958 PASS, normalized_dev 54/54 PASS (no regressions)

Design: Dual-path (BindingId OR name) enables gradual Phase 77+ transition.

🤖 Generated with Claude Code

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

src/mir/join_ir/normalized/fixtures.rs

@@ -104,6 +104,8 @@ pub fn build_pattern2_minimal_structured() -> JoinModule {
         carriers: vec![],
         trim_helper: None,
         promoted_loopbodylocals: vec![],
+        #[cfg(feature = "normalized_dev")]
+        promoted_bindings: std::collections::BTreeMap::new(),
     };
 
     let carrier_updates: BTreeMap<String, UpdateExpr> = BTreeMap::new();