docs: update CURRENT_TASK with Box Theory PHI plan (defer/finalize) and MIR v0.5 type meta; add parity tooling and PyVM scaffolding

impl(pyvm/llvmlite):
- add tools/parity.sh; tools/pyvm_runner.py; src/llvm_py/pyvm/*
- emit string const as handle type in MIR JSON; add dst_type hints
- unify '+' to concat_hh with from_i64/from_i8_string bridges; console print via to_i8p_h
- add runtime bridges: nyash.box.from_i64, nyash.string.to_i8p_h

tests:
- add apps/tests/min_str_cat_loop (minimal repro for string cat loop)

src/llvm_py/resolver.py

@@ -33,6 +33,8 @@ class Resolver:
         self.f64_cache: Dict[Tuple[str, int], ir.Value] = {}
         # String literal map: value_id -> Python string (for by-name calls)
         self.string_literals: Dict[int, str] = {}
+        # Optional: value_id -> i8* pointer for string constants (lower_const can populate)
+        self.string_ptrs: Dict[int, ir.Value] = {}
         # Track value-ids that are known to represent string handles (i64)
         # This is a best-effort tag used to decide '+' as string concat when both sides are i64.
         self.string_ids: set[int] = set()