Correct `to_actor.run()` target guidance

Target validation moved to a follow-up branch, so the guide should not
claim unstable callable forms are rejected before actor startup.

Describe module-global functions and `functools.partial()` wrappers
as portable stable-address forms without promising absent enforcement.

(this patch was generated in some part by `opencode` using
`gpt-5.6-sol` (`openai`))

ai/prompt-io/opencode/20260820T150250Z_9afda1c6_prompt_io.md

@@ -1,33 +0,0 @@
----
-model: openai/gpt-5.6-sol
-service: opencode
-session: 7b9c97c4-fff7-4ac4-97fb-35720453308e
-timestamp: 2026-08-20T15:02:50Z
-git_ref: pformat_caller_frame_render_guard
-scope: code
-substantive: true
-raw_file: 20260820T150250Z_9afda1c6_prompt_io.raw.md
----
-
-## Prompt
-
-Fix both newly exposed send-side `MsgTypeError` formatting failures
-and pin them with an end-to-end regression in PR #503.
-
-## Response summary
-
-Corrected codec-spec formatting and default error-message assembly so
-`_mk_send_mte()` returns a printable error instead of raising another
-formatter exception.
-
-## Files changed
-
-- `tractor/msg/_codec.py` - pass the codec to its supported formatter.
-- `tractor/_exceptions.py` - assemble the default message as `str`.
-- `tests/devx/test_pformat.py` - render the complete default error.
-
-## Human edits
-
-The human selected both one-line fixes and the single end-to-end test
-as coherent additions to PR #503, while leaving broader formatter
-cleanup out of scope.

ai/prompt-io/opencode/20260820T150250Z_9afda1c6_prompt_io.raw.md

@@ -1,25 +0,0 @@
----
-model: openai/gpt-5.6-sol
-service: opencode
-timestamp: 2026-08-20T15:02:50Z
-git_ref: pformat_caller_frame_render_guard
-diff_cmd: git diff HEAD~1..HEAD
----
-
-## Prompt
-
-After reviewing additional `tractor.devx.pformat` work suitable for
-PR #503, the user approved fixing both send-side `MsgTypeError`
-formatting failures and adding an end-to-end regression.
-
-## Response
-
-The generated code corrects the `MsgCodec.msg_spec_str` formatter
-input, keeps `_mk_send_mte()`'s assembled default message a string,
-and tests that the resulting `MsgTypeError` can be rendered:
-
-> `git diff HEAD~1..HEAD -- tractor/msg/_codec.py tractor/_exceptions.py tests/devx/test_pformat.py`
-
-These failures were hidden behind the original
-`pformat_caller_frame()` keyword error addressed by the first two
-commits on the branch.

tests/devx/test_pformat.py

@@ -1,84 +0,0 @@
-'''
-Unit tests for the `tractor.devx.pformat` render helpers.
-
-'''
-from __future__ import annotations
-
-import pytest
-
-from tractor._exceptions import _mk_send_mte
-from tractor.devx.pformat import (
-    pformat_boxed_tb,
-    pformat_caller_frame,
-)
-from tractor.msg._codec import _def_tractor_codec
-
-
-@pytest.mark.parametrize(
-    'box_tb',
-    [True, False],
-    ids=['boxed', 'bare'],
-)
-def test_pformat_caller_frame_renders(box_tb: bool):
-    '''
-    `pformat_caller_frame()` must render, not raise.
-
-    XXX the `box_tb=True` branch was passing an `indent=''` kwarg
-    that `pformat_boxed_tb()` never accepted, so it blew up with
-    a `TypeError`. Nothing in the test suite covered it, and the
-    only caller is `_mk_send_mte()` — i.e. EVERY send-side
-    `MsgTypeError` died while formatting itself, masking the real
-    msg-spec violation behind a bogus `TypeError`.
-
-    '''
-    report: str = pformat_caller_frame(
-        stack_limit=3,
-        box_tb=box_tb,
-    )
-    assert isinstance(report, str)
-    assert 'test_pformat_caller_frame_renders' in report
-
-
-def test_pformat_boxed_tb_rejects_unknown_kwargs():
-    '''
-    Pin the signature so a future typo'd kwarg fails loudly at the
-    call site rather than only when some rare error path runs.
-
-    '''
-    assert pformat_boxed_tb(tb_str='doggy\n')
-
-    with pytest.raises(TypeError):
-        pformat_boxed_tb(
-            tb_str='doggy\n',
-            indent='',
-        )
-
-
-def test_send_mte_default_message_renders():
-    '''
-    The default send-side `MsgTypeError` must remain printable.
-
-    Once `pformat_caller_frame()` stopped failing first, this path
-    exposed two more formatter errors: `MsgCodec.msg_spec_str` passed
-    a type union where `pformat_msgspec()` requires a codec/decoder,
-    then `_mk_send_mte()` wrapped its message in a one-element tuple.
-
-    Construct the error without an override message to execute that
-    complete default path. Requiring a `str` message with the bad
-    value and valid spec, then rendering the exception, proves the
-    original IPC violation survives every formatter layer.
-
-    '''
-    bad_msg: dict[str, bool] = {'bad': True}
-    mte = _mk_send_mte(
-        msg=bad_msg,
-        codec=_def_tractor_codec,
-    )
-
-    assert isinstance(mte.message, str)
-    assert f'invalid msg -> {bad_msg}' in mte.message
-    assert 'Valid IPC msgs are:' in mte.message
-
-    report: str = repr(mte)
-    assert 'MsgTypeError' in report
-    assert f'invalid msg -> {bad_msg}' in report

tractor/_exceptions.py

@@ -1509,7 +1509,7 @@ def _mk_send_mte(
             f'invalid msg -> {msg}: {type(msg)}\n\n'
             f'{tb_fmt}\n'
             f'Valid IPC msgs are:\n\n'
-            f'{codec.msg_spec_str}\n'
+            f'{codec.msg_spec_str}\n',
         )
     elif src_type_error:
         src_message: str = str(src_type_error)

tractor/devx/pformat.py

@@ -215,6 +215,7 @@ def pformat_caller_frame(
         tb_str: str = pformat_boxed_tb(
             tb_str=tb_str,
             field_prefix='  ',
+            indent='',
         )
     return tb_str
 

tractor/msg/_codec.py

@@ -430,7 +430,7 @@ class MsgCodec(Struct):
     # wrapped field over the `.msg_spec` one?
     @property
     def msg_spec_str(self) -> str:
-        return pformat_msgspec(self)
+        return pformat_msgspec(self.msg_spec)
 
     lib: ModuleType = msgspec