Move runtime frame hiding into helper func

Call it `hide_runtime_frames()` and stick all the lines from the top of
the `._debug` mod in there along with a little `log.devx()` emission on
what gets hidden by default ;)

Other,
- fix ref-error where internal-error handler might trigger despite the
  debug `req_ctx` not yet having init-ed, such that we don't try to
  cancel or log about it when it never was fully created/initialize..
- fix assignment typo iniside `_set_trace()` for `task`.. lel

tractor/devx/_debug.py

@@ -48,9 +48,11 @@ from typing import (
     TYPE_CHECKING,
 )
 from types import (
+    FunctionType,
     FrameType,
     ModuleType,
     TracebackType,
+    CodeType,
 )
 
 from msgspec import Struct
@@ -90,6 +92,14 @@ if TYPE_CHECKING:
 
 log = get_logger(__name__)
 
+
+def hide_runtime_frames() -> dict[FunctionType, CodeType]:
+    '''
+    Hide call-stack frames for various std-lib and `trio`-API primitives
+    such that the tracebacks presented from our runtime are as minimized
+    as possible, particularly from inside a `PdbREPL`.
+
+    '''
     # XXX HACKZONE XXX
     #  hide exit stack frames on nurseries and cancel-scopes!
     # |_ so avoid seeing it when the `pdbp` REPL is first engaged from
@@ -117,16 +127,37 @@ log = get_logger(__name__)
     # -[ ] maybe dig into the core `pdb` issue why the extra frame is shown
     #      at all?
     #
-pdbp.hideframe(trio._core._run.NurseryManager.__aexit__)
-pdbp.hideframe(trio._core._run.CancelScope.__exit__)
-pdbp.hideframe(_GeneratorContextManager.__exit__)
-pdbp.hideframe(_AsyncGeneratorContextManager.__aexit__)
-pdbp.hideframe(trio.Event.wait)
-
-__all__ = [
-    'breakpoint',
-    'post_mortem',
+    funcs: list[FunctionType] = [
+        trio._core._run.NurseryManager.__aexit__,
+        trio._core._run.CancelScope.__exit__,
+         _GeneratorContextManager.__exit__,
+         _AsyncGeneratorContextManager.__aexit__,
+         _AsyncGeneratorContextManager.__aenter__,
+         trio.Event.wait,
     ]
+    func_list_str: str = textwrap.indent(
+        "\n".join(f.__qualname__ for f in funcs),
+        prefix=' |_ ',
+    )
+    log.devx(
+        'Hiding the following runtime frames by default:\n'
+        f'{func_list_str}\n'
+    )
+
+    codes: dict[FunctionType, CodeType] = {}
+    for ref in funcs:
+        # stash a pre-modified version of each ref's code-obj
+        # so it can be reverted later if needed.
+        codes[ref] = ref.__code__
+        pdbp.hideframe(ref)
+    #
+    # pdbp.hideframe(trio._core._run.NurseryManager.__aexit__)
+    # pdbp.hideframe(trio._core._run.CancelScope.__exit__)
+    # pdbp.hideframe(_GeneratorContextManager.__exit__)
+    # pdbp.hideframe(_AsyncGeneratorContextManager.__aexit__)
+    # pdbp.hideframe(_AsyncGeneratorContextManager.__aenter__)
+    # pdbp.hideframe(trio.Event.wait)
+    return codes
 
 
 class LockStatus(
@@ -1032,15 +1063,24 @@ async def request_root_stdio_lock(
 
             except (
                 BaseException,
-            ):
-                log.exception(
-                    'Failed during root TTY-lock dialog?\n'
-                    f'{req_ctx}\n'
+            ) as ctx_err:
+                message: str = (
+                    'Failed during debug request dialog with root actor?\n\n'
+                )
 
+                if req_ctx:
+                    message += (
+                        f'{req_ctx}\n'
                         f'Cancelling IPC ctx!\n'
                     )
                     await req_ctx.cancel()
-                raise
+
+                else:
+                    message += 'Failed during `Portal.open_context()` ?\n'
+
+                log.exception(message)
+                ctx_err.add_note(message)
+                raise ctx_err
 
 
     except (
@@ -1067,6 +1107,7 @@ async def request_root_stdio_lock(
         #   ctl-c out of the currently hanging task! 
         raise DebugRequestError(
             'Failed to lock stdio from subactor IPC ctx!\n\n'
+
             f'req_ctx: {DebugStatus.req_ctx}\n'
         ) from req_err
 
@@ -1777,7 +1818,7 @@ def _set_trace(
 ):
     __tracebackhide__: bool = hide_tb
     actor: tractor.Actor = actor or current_actor()
-    task: task or current_task()
+    task: trio.Task = task or current_task()
 
     # else:
     # TODO: maybe print the actor supervion tree up to the