Move getOrCreateJniSlots (the cls/methodid slot-cache builder) out of
emit_llvm.zig into the FfiCtors backend *LLVMEmitter facade. Behavior-preserving
— self.* -> self.e.* only.
- FfiCtors gains getOrCreateJniSlots (pub). The jni_slots cache + mangleJniKey
stay on LLVMEmitter; mangleJniKey is widened to pub (the facade calls it back,
like lazyDeclareCRuntime/emitPrivateCString), and JniSlotPair is widened to pub
(the facade returns it; the call site consumes it). 1 call site routed via
ffiCtors().
- emitJniConstructor intentionally NOT moved in this slice: it is emission-heavy
(resolveRef/mapRef/coerceArg/getRefIRType/extractSlicePtr/loadJniFn/
emitCStringGlobal — 100+ internal callers for the first two), so relocating it
would pub-expose the emitter's core value-emission machinery. Consistent with
A7.2 keeping emitFieldValueGet in emit_llvm.zig. Pending an explicit decision.
Gate: zig build, zig build test, bash tests/run_examples.sh -> 361/0
(JNI anchors 1402/1408/1418/1425 green, no churn).