root.zig had no `test` block, so the test binary discovered zero tests and
trivially "passed" — every src test had silently rotted. Add
`refAllDecls(@This())` to root.zig so all 185 tests run, then fix the rot it
surfaced:
- emit_llvm.test: operands were constants, so LLVM folded the very
instructions being asserted (fadd/sub/icmp/insertvalue/extractvalue/sext).
Rewrite to use function-parameter operands; `main` now returns i32 (entry
convention); tagged-union enum_init lowers via memory, not insertvalue.
- interp.test: switch the per-test allocator to an arena (the interpreter is
arena-style and intentionally frees little) — clears the transient-Value
leaks without an ownership-ambiguous source change.
- lower.test: pass `is_imported` to lowerFunction; mark two helpers `pub`; the
if/else block test now uses a runtime (param) condition since lowering folds
`if true`.
- print.test: SSA numbering — params occupy %0/%1, so consts start at %2.
- jni_java_emit.test: nested-class refs render in Java source form
(`SurfaceHolder.Callback`), not the JNI `$` form.
Leaks fixed at the source where ownership was clear: Module gains an arena for
the operand slices the Builder dupes (struct/call/branch/switch args, block
params, lowerFunction params); objcDefinedStateStructType builds its field
slice in that arena and frees its temp name string.
