Call `.devx._debug.hide_runtime_frames()` by default

From both `open_root_actor()` and `._entry._trio_main()`.

Other `breakpoint()`-from-sync-func fixes:
- properly disable the default hook using `"0"` XD
- offer a `hide_tb: bool` from `open_root_actor()`.
- disable hiding the `._trio_main()` frame, bc pretty sure it doesn't
  help anyone (either way) when REPL-ing/tb-ing from a subactor..?

tractor/_entry.py

@@ -33,6 +33,7 @@ from .log import (
     get_logger,
 )
 from . import _state
+from .devx import _debug
 from .to_asyncio import run_as_asyncio_guest
 from ._runtime import (
     async_main,
@@ -96,7 +97,6 @@ def _mp_main(
 
 
 def _trio_main(
-
     actor: Actor,
     *,
     parent_addr: tuple[str, int] | None = None,
@@ -107,7 +107,9 @@ def _trio_main(
     Entry point for a `trio_run_in_process` subactor.
 
     '''
-    __tracebackhide__: bool = True
+    # __tracebackhide__: bool = True
+    _debug.hide_runtime_frames()
+
     _state._current_actor = actor
     trio_main = partial(
         async_main,
@@ -146,7 +148,6 @@ def _trio_main(
             +
             actor_info
         )
-
     finally:
         log.info(
             'Subactor terminated\n'

tractor/_root.py

@@ -91,12 +91,16 @@ async def open_root_actor(
     # and that this call creates it.
     ensure_registry: bool = False,
 
+    hide_tb: bool = True,
+
 ) -> Actor:
     '''
     Runtime init entry point for ``tractor``.
 
     '''
-    __tracebackhide__ = True
+    __tracebackhide__: bool = hide_tb
+    _debug.hide_runtime_frames()
+
     # TODO: stick this in a `@cm` defined in `devx._debug`?
     #
     # Override the global debugger hook to make it play nice with
@@ -125,7 +129,7 @@ async def open_root_actor(
         # usage by a clobbered TTY's stdstreams!
         def block_bps(*args, **kwargs):
             raise RuntimeError(
-                'Trying to use `breakpoint()` eh?\n'
+                'Trying to use `breakpoint()` eh?\n\n'
                 'Welp, `tractor` blocks `breakpoint()` built-in calls by default!\n'
                 'If you need to use it please install `greenback` and set '
                 '`debug_mode=True` when opening the runtime '
@@ -133,7 +137,9 @@ async def open_root_actor(
             )
 
         sys.breakpointhook = block_bps
-        # os.environ['PYTHONBREAKPOINT'] = None
+        # lol ok,
+        # https://docs.python.org/3/library/sys.html#sys.breakpointhook
+        os.environ['PYTHONBREAKPOINT'] = "0"
 
     # attempt to retreive ``trio``'s sigint handler and stash it
     # on our debugger lock state.
@@ -203,6 +209,7 @@ async def open_root_actor(
         ):
             loglevel = 'PDB'
 
+
     elif debug_mode:
         raise RuntimeError(
             "Debug mode is only supported for the `trio` backend!"