Expand bytecode expressions and loops

notes/bytecode_exprs_loops.md

@@ -0,0 +1,11 @@
+# Bytecode expression + for-in loop support
+
+Changes
+- Added bytecode compilation for conditional/elvis expressions, inc/dec, and compound assignments where safe.
+- Added ForInStatement and ConstIntRange to keep for-loop structure explicit (no anonymous Statement).
+- Added PUSH_SCOPE/POP_SCOPE opcodes with SlotPlan constants to create loop scopes in bytecode.
+- Bytecode compiler emits int-range for-in loops when const range is known and no break/continue.
+
+Tests
+- ./gradlew :lynglib:jvmTest
+- ./gradlew :lynglib:allTests -x :lynglib:jvmTest