Add test for non-registrar root sub-spawning

Ensure non-registrar root actors can spawn children and that
those children receive correct parent contact info. This test
catches the bug reported in,

https://github.com/goodboy/tractor/issues/410

Add new `test_non_registrar_spawns_child()` which spawns a sub-actor
from a non-registrar root and verifies the child can manually connect
back to its parent using `get_root()` API, auditing
`._state._runtime_vars` addr propagation from rent to child.

Also,
- improve type hints throughout test suites
  (`subprocess.Popen`, `UnwrappedAddress`, `Aid` etc.)
- rename `n` -> `an` for actor nursery vars
- use multiline style for function signatures

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

tests/test_multi_program.py

@@ -1,8 +1,13 @@
 """
 Multiple python programs invoking the runtime.
 """
+from __future__ import annotations
 import platform
+import subprocess
 import time
+from typing import (
+    TYPE_CHECKING,
+)
 
 import pytest
 import trio
@@ -10,14 +15,27 @@ import tractor
 from tractor._testing import (
     tractor_test,
 )
+from tractor import (
+    Actor,
+    Context,
+    Portal,
+)
 from .conftest import (
     sig_prog,
     _INT_SIGNAL,
     _INT_RETURN_CODE,
 )
 
+if TYPE_CHECKING:
+    from tractor.msg import Aid
+    from tractor._addr import (
+        UnwrappedAddress,
+    )
 
-def test_abort_on_sigint(daemon):
+
+def test_abort_on_sigint(
+    daemon: subprocess.Popen,
+):
     assert daemon.returncode is None
     time.sleep(0.1)
     sig_prog(daemon, _INT_SIGNAL)
@@ -30,7 +48,10 @@ def test_abort_on_sigint(daemon):
 
 
 @tractor_test
-async def test_cancel_remote_arbiter(daemon, reg_addr):
+async def test_cancel_remote_arbiter(
+    daemon: subprocess.Popen,
+    reg_addr: UnwrappedAddress,
+):
     assert not tractor.current_actor().is_arbiter
     async with tractor.get_registry(reg_addr) as portal:
         await portal.cancel_actor()
@@ -45,24 +66,84 @@ async def test_cancel_remote_arbiter(daemon, reg_addr):
             pass
 
 
-def test_register_duplicate_name(daemon, reg_addr):
-
+def test_register_duplicate_name(
+    daemon: subprocess.Popen,
+    reg_addr: UnwrappedAddress,
+):
     async def main():
-
         async with tractor.open_nursery(
             registry_addrs=[reg_addr],
-        ) as n:
+        ) as an:
 
             assert not tractor.current_actor().is_arbiter
 
-            p1 = await n.start_actor('doggy')
-            p2 = await n.start_actor('doggy')
+            p1 = await an.start_actor('doggy')
+            p2 = await an.start_actor('doggy')
 
             async with tractor.wait_for_actor('doggy') as portal:
                 assert portal.channel.uid in (p2.channel.uid, p1.channel.uid)
 
-            await n.cancel()
+            await an.cancel()
 
-    # run it manually since we want to start **after**
-    # the other "daemon" program
+    # XXX, run manually since we want to start this root **after**
+    # the other "daemon" program with it's own root.
+    trio.run(main)
+
+
+@tractor.context
+async def get_root_portal(
+    ctx: Context,
+):
+    '''
+    Connect back to the root actor manually (using `._discovery` API)
+    and ensure it's contact info is the same as our immediate parent.
+
+    '''
+    await ctx.started()
+    from tractor._discovery import get_root
+    ptl: Portal
+    async with get_root() as ptl:
+        root_aid: Aid = ptl.chan.aid
+        parent_ptl: Portal = tractor.current_actor().get_parent()
+        assert (
+            root_aid.name == 'root'
+            and
+            parent_ptl.chan.aid == root_aid
+        )
+
+
+def test_non_registrar_spawns_child(
+    daemon: subprocess.Popen,
+    reg_addr: UnwrappedAddress,
+):
+    '''
+    Ensure a non-regristar (serving) root actor can spawn a sub and
+    that sub can connect back (manually) to it's rent that is the
+    root without issue.
+
+    More or less this audits the global contact info in
+    `._state._runtime_vars`.
+
+    '''
+    async def main():
+        async with tractor.open_nursery(
+            registry_addrs=[reg_addr],
+        ) as an:
+
+            actor: Actor = tractor.current_actor()
+            assert not actor.is_registrar
+            sub_ptl: Portal = await an.start_actor(
+                name='sub',
+                enable_modules=[__name__],
+            )
+
+            async with sub_ptl.open_context(
+                get_root_portal,
+            ) as (ctx, first):
+                pass
+
+            await an.cancel()
+
+    # XXX, run manually since we want to start this root **after**
+    # the other "daemon" program with it's own root.
     trio.run(main)