New execution mode: ./run vm <file.j> compiles AST to bytecodes and
runs them in a while/switch loop. Ints/floats live on the stack (no
heap allocation), ~7.7x faster than the tree-walking interpreter.
Implements: opcodes, compiler with backpatching (if/while), stack VM
with arithmetic, comparisons, variables, strings, and print/println.
Reorganizes backend into src/backend/eval/ and src/backend/bytecode/.
- Lexer: add INDENT/DEDENT tokens, <, >, : operators, while keyword,
closing DEDENT emission, include guards
- Parser: add NODE_WHILE with while_loop union, parse while/cond/body
blocks, include guards
- Eval: add while loop evaluation, GC integration with roots from env,
debug and gc flags, <, > comparison operators
- GC: implement mark-and-sweep collector with 3 stages (mark roots,
sweep unmarked, join free blocks)
- Allocator: block reuse via first-fit search with splitting, exponential
heap growth, NULL check on malloc, include guards, marked field in metadata
- Object: add include guards, fix include to use allocator.h
- Implement OBJ_LIST with offset-based items array and capacity
- obj_free now releases child allocations (string buffer, list items)
- obj_print detects self-referencing lists to prevent infinite recursion
- Visualizer distinguishes freed blocks (JLANG_NOT_USE) from active ones
- JLANG_free now zeroes payload on release
JLANG_malloc now returns size_t offsets relative to the heap buffer,
making all references stable across heap growth (realloc). Object API
updated accordingly: constructors return offsets, obj_print/obj_free
receive (allocator, offset). Added heap auto-grow when out of space.
