Expose `RuntimeVars` + `get_runtime_vars()` from pkg

Export the new `RuntimeVars` struct and `get_runtime_vars()`
from `tractor.__init__` and improve the accessor to
optionally return the struct form.

Deats,
- add `RuntimeVars` and `get_runtime_vars` to
  `__init__.py` exports; alphabetize `_state` imports.
- move `get_runtime_vars()` up in `_state.py` to sit
  right below `_runtime_vars` dict definition.
- add `as_dict: bool = True` param so callers can get
  either the legacy `dict` or the new `RuntimeVars`
  struct.
- drop the old stub fn at bottom of `_state.py`.
- rm stale `from .msg.pretty_struct import Struct` comment.

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

tractor/__init__.py

@@ -41,10 +41,12 @@ from ._supervise import (
     ActorNursery as ActorNursery,
 )
 from ._state import (
+    RuntimeVars as RuntimeVars,
     current_actor as current_actor,
-    is_root_process as is_root_process,
     current_ipc_ctx as current_ipc_ctx,
-    debug_mode as debug_mode
+    debug_mode as debug_mode,
+    get_runtime_vars as get_runtime_vars,
+    is_root_process as is_root_process,
 )
 from ._exceptions import (
     ContextCancelled as ContextCancelled,

tractor/_state.py

@@ -33,7 +33,6 @@ from typing import (
 import platformdirs
 from trio.lowlevel import current_task
 
-# from .msg.pretty_struct import Struct
 from msgspec import (
     field,
     Struct,
@@ -54,6 +53,7 @@ _def_tpt_proto: TransportProtocolKey = 'tcp'
 _current_actor: Actor|None = None  # type: ignore # noqa
 _last_actor_terminated: Actor|None = None
 
+
 # TODO: mk this a `msgspec.Struct`!
 # -[x] type out all fields obvi!
 # -[ ] (eventually) mk wire-ready for monitoring?
@@ -140,6 +140,23 @@ _runtime_vars: dict[str, Any] = {
 }
 
 
+def get_runtime_vars(
+    as_dict: bool = True,
+) -> dict:
+    '''
+    Deliver a **copy** of the current `Actor`'s "runtime variables".
+
+    By default, for historical impl reasons, this delivers the `dict`
+    form, but the `RuntimeVars` struct should be utilized as possible
+    for future calls.
+
+    '''
+    if as_dict:
+        return dict(_runtime_vars)
+
+    return RuntimeVars(**_runtime_vars)
+
+
 def last_actor() -> Actor|None:
     '''
     Try to return last active `Actor` singleton
@@ -301,12 +318,3 @@ def current_ipc_protos() -> list[str]:
 
     '''
     return _runtime_vars['_enable_tpts']
-
-
-# !TODO, convert this to the new `RuntimeVars` struct!
-def get_runtime_vars() -> dict:
-    '''
-    Deliver a **copy** of the current `Actor`'s "runtime variables".
-
-    '''
-    return dict(_runtime_vars)