public: publish selfhost snapshot to public repo (SSOT using + AST merge + JSON VM fixes)

- SSOT using profiles (aliases/packages via nyash.toml), AST prelude merge
- Parser/member guards; Builder pin/PHI and instance→function rewrite (dev on)
- VM refactors (handlers split) and JSON roundtrip/nested stabilization
- CURRENT_TASK.md updated with scope and acceptance criteria

Notes: dev-only guards remain togglable via env; no default behavior changes for prod.

src/backend/mir_interpreter/mod.rs

@@ -24,7 +24,8 @@ mod helpers;
 pub struct MirInterpreter {
     pub(super) regs: HashMap<ValueId, VMValue>,
     pub(super) mem: HashMap<ValueId, VMValue>,
-    pub(super) obj_fields: HashMap<ValueId, HashMap<String, VMValue>>,
+    // Object field storage keyed by stable object identity (Arc ptr addr fallback)
+    pub(super) obj_fields: HashMap<u64, HashMap<String, VMValue>>,
     pub(super) functions: HashMap<String, MirFunction>,
     pub(super) cur_fn: Option<String>,
     // Trace context (dev-only; enabled with NYASH_VM_TRACE=1)