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)

crates/nyrt/src/plugin/string.rs

@@ -83,7 +83,7 @@ pub extern "C" fn nyash_string_concat_is(a: i64, b: *const i8) -> *mut i8 {
 // Exported as: nyash.string.substring_sii(i8* s, i64 start, i64 end) -> i8*
 #[export_name = "nyash.string.substring_sii"]
 pub extern "C" fn nyash_string_substring_sii(s: *const i8, start: i64, end: i64) -> *mut i8 {
-    use std::ffi::CStr;
+use std::ffi::CStr;
     if s.is_null() {
         return std::ptr::null_mut();
     }
@@ -121,3 +121,34 @@ pub extern "C" fn nyash_string_lastindexof_ss(s: *const i8, needle: *const i8) -
         pos as i64
     } else { -1 }
 }
+
+// Exported as: nyash.string.to_i8p_h(i64 handle) -> i8*
+#[export_name = "nyash.string.to_i8p_h"]
+pub extern "C" fn nyash_string_to_i8p_h(handle: i64) -> *mut i8 {
+    use nyash_rust::jit::rt::handles;
+    if handle <= 0 {
+        // return "0" for consistency with existing fallback behavior
+        let s = handle.to_string();
+        let mut bytes = s.into_bytes();
+        bytes.push(0);
+        let boxed = bytes.into_boxed_slice();
+        let raw = Box::into_raw(boxed) as *mut u8;
+        return raw as *mut i8;
+    }
+    if let Some(obj) = handles::get(handle as u64) {
+        let s = obj.to_string_box().value;
+        let mut bytes = s.into_bytes();
+        bytes.push(0);
+        let boxed = bytes.into_boxed_slice();
+        let raw = Box::into_raw(boxed) as *mut u8;
+        raw as *mut i8
+    } else {
+        // not found -> print numeric handle string
+        let s = handle.to_string();
+        let mut bytes = s.into_bytes();
+        bytes.push(0);
+        let boxed = bytes.into_boxed_slice();
+        let raw = Box::into_raw(boxed) as *mut u8;
+        raw as *mut i8
+    }
+}