Tighten UDS addr validation and sockname prefixes

- add `is_valid` and `sockpath.resolve()` asserts in
  `get_rando_addr()` for the `'uds'` case plus an
  explicit `UDSAddress` type annotation.
- rename no-runtime sockname prefixes from
  `'<unknown-actor>'`/`'root'` to
  `'no_runtime_root'`/`'no_runtime_actor'` with a proper
  if/else branch in `UDSAddress.get_random()`.

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

tractor/_testing/addr.py

@@ -61,7 +61,11 @@ def get_rando_addr(
         # NOTE, file-name uniqueness (no-collisions) will be based on
         # the runtime-directory and root (pytest-proc's) pid.
         case 'uds':
-            testrun_reg_addr = addr_type.get_random().unwrap()
+            from tractor.ipc._uds import UDSAddress
+            addr: UDSAddress = addr_type.get_random()
+            assert addr.is_valid
+            assert addr.sockpath.resolve()
+            testrun_reg_addr = addr.unwrap()
 
     # XXX, as sanity it should never the same as the default for the
     # host-singleton registry actor.

tractor/ipc/_uds.py

@@ -197,9 +197,11 @@ class UDSAddress(
             # sockname: str = '.'.join(actor.uid) + f'@{pid}'
             # -[ ] CURRENTLY using `.` BREAKS TEST SUITE tho..
         else:
-            prefix: str = '<unknown-actor>'
             if is_root_process():
-                prefix: str = 'root'
+                prefix: str = 'no_runtime_root'
+            else:
+                prefix: str = 'no_runtime_actor'
+
             sockname: str = f'{prefix}@{pid}'
 
         sockpath: Path = Path(f'{sockname}.sock')