Use `Context._stream` in `_raise_from_unexpected_msg()`

Instead of expecting it to be passed in (as it was prior), when
determining if a `Stop` msg is a valid end-of-channel signal use the
`ctx._stream: MsgStream|None` attr which **must** be set by any stream
opening API; either of:
- `Context.open_stream()`
- `Portal.open_stream_from()`

Adjust the case block logic to match with fallthrough from any EoC to
a closed error if necessary. Change the `_type: str` to match the
failing IPC-prim name in the tail case we raise a `MessagingError`.

Other:
- move `.sender: tuple` uid attr up to `RemoteActorError` since `Error`
  optionally defines it as a field and for boxed `StreamOverrun`s (an
  ignore case we check for in the runtime during cancellation) we want
  it readable from the boxing rae.
- drop still unused `InternalActorError`.

tractor/_exceptions.py

@@ -532,7 +532,8 @@ class RemoteActorError(Exception):
         self,
     ) -> BaseException:
         '''
-        Unpack the inner-most source error from it's original IPC msg data.
+        Unpack the inner-most source error from it's original IPC
+        msg data.
 
         We attempt to reconstruct (as best as we can) the original
         `Exception` from as it would have been raised in the
@@ -570,6 +571,14 @@ class RemoteActorError(Exception):
     #     #     boxed_type=get_type_ref(..
     #     raise NotImplementedError
 
+    @property
+    def sender(self) -> tuple[str, str]|None:
+        if (
+            (msg := self._ipc_msg)
+            and (value := msg.sender)
+        ):
+            return tuple(value)
+
 
 class ContextCancelled(RemoteActorError):
     '''
@@ -734,20 +743,6 @@ class StreamOverrun(
     handled by app code using `MsgStream.send()/.receive()`.
 
     '''
-    @property
-    def sender(self) -> tuple[str, str] | None:
-        value = self._ipc_msg.sender
-        if value:
-            return tuple(value)
-
-
-# class InternalActorError(RemoteActorError):
-#     '''
-#     Boxed (Remote) internal `tractor` error indicating failure of some
-#     primitive, machinery state or lowlevel task that should never
-#     occur.
-
-#     '''
 
 
 class TransportClosed(trio.ClosedResourceError):
@@ -945,7 +940,6 @@ def _raise_from_unexpected_msg(
     log: StackLevelAdapter,  # caller specific `log` obj
 
     expect_msg: str = Yield,
-    stream: MsgStream | None = None,
 
     # allow "deeper" tbs when debugging B^o
     hide_tb: bool = True,
@@ -987,6 +981,8 @@ def _raise_from_unexpected_msg(
         ) from src_err
 
     # TODO: test that shows stream raising an expected error!!!
+    stream: MsgStream|None
+    _type: str = 'Context'
 
     # raise the error message in a boxed exception type!
     if isinstance(msg, Error):
@@ -1003,55 +999,50 @@ def _raise_from_unexpected_msg(
     # TODO: does it make more sense to pack 
     # the stream._eoc outside this in the calleer always?
         # case Stop():
-    elif (
-        isinstance(msg, Stop)
-        or (
-            stream
-            and stream._eoc
-        )
-    ):
-        log.debug(
-            f'Context[{cid}] stream was stopped by remote side\n'
-            f'cid: {cid}\n'
-        )
+    elif stream := ctx._stream:
+        _type: str = 'MsgStream'
 
-        # TODO: if the a local task is already blocking on
-        # a `Context.result()` and thus a `.receive()` on the
-        # rx-chan, we close the chan and set state ensuring that
-        # an eoc is raised!
+        if (
+            stream._eoc
+            or
+            isinstance(msg, Stop)
+        ):
+            log.debug(
+                f'Context[{cid}] stream was stopped by remote side\n'
+                f'cid: {cid}\n'
+            )
 
-        # XXX: this causes ``ReceiveChannel.__anext__()`` to
-        # raise a ``StopAsyncIteration`` **and** in our catch
-        # block below it will trigger ``.aclose()``.
-        eoc = trio.EndOfChannel(
-            f'Context stream ended due to msg:\n\n'
-            f'{pformat(msg)}\n'
-        )
-        # XXX: important to set so that a new `.receive()`
-        # call (likely by another task using a broadcast receiver)
-        # doesn't accidentally pull the `return` message
-        # value out of the underlying feed mem chan which is
-        # destined for the `Context.result()` call during ctx-exit!
-        stream._eoc: Exception = eoc
+            # TODO: if the a local task is already blocking on
+            # a `Context.result()` and thus a `.receive()` on the
+            # rx-chan, we close the chan and set state ensuring that
+            # an eoc is raised!
 
-        # in case there already is some underlying remote error
-        # that arrived which is probably the source of this stream
-        # closure
-        ctx.maybe_raise()
-        raise eoc from src_err
+            # XXX: this causes ``ReceiveChannel.__anext__()`` to
+            # raise a ``StopAsyncIteration`` **and** in our catch
+            # block below it will trigger ``.aclose()``.
+            eoc = trio.EndOfChannel(
+                f'Context stream ended due to msg:\n\n'
+                f'{pformat(msg)}\n'
+            )
+            # XXX: important to set so that a new `.receive()`
+            # call (likely by another task using a broadcast receiver)
+            # doesn't accidentally pull the `return` message
+            # value out of the underlying feed mem chan which is
+            # destined for the `Context.result()` call during ctx-exit!
+            stream._eoc: Exception = eoc
 
-    if (
-        stream
-        and stream._closed
-    ):
-        # TODO: our own error subtype?
-        raise trio.ClosedResourceError(
-            'This stream was closed'
-        )
+            # in case there already is some underlying remote error
+            # that arrived which is probably the source of this stream
+            # closure
+            ctx.maybe_raise()
+            raise eoc from src_err
+
+        if stream._closed:
+            # TODO: our own error subtype?
+            raise trio.ClosedResourceError('This stream was closed')
 
     # always re-raise the source error if no translation error case
     # is activated above.
-    _type: str = 'Stream' if stream else 'Context'
     raise MessagingError(
         f"{_type} was expecting a {expect_msg} message"
         " BUT received a non-error msg:\n"