Strengthen context and debugger regressions

Older review threads found that context startup mocks did not identify
the internal cancel RPC, the overrun packer seam lacked rationale and
the debugger test no longer asserted its KeyboardInterrupt transcript.

Assert exact startup/cancel RPC ordering, explain the stable error spy,
add terse test typing and restore the terminal interrupt check after
EOF.

Review: PR #481 (goodboy)
https://github.com/goodboy/tractor/pull/481#pullrequestreview-5012942328

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

tests/devx/test_debugger.py

@@ -1359,6 +1359,8 @@ def test_ctxep_pauses_n_maybe_ipc_breaks(
                 expect_prompt=False,
             )
             child.expect(EOF)
+            before += ansi_strip(child.before.decode())
+            assert 'KeyboardInterrupt' in before
             assert child.flag_eof
             assert not child.isalive()
 

tests/test_context_stream_semantics.py

@@ -86,7 +86,7 @@ from ._helpers import (
 
 def test_overrun_error_send_tolerates_transport_close(
     monkeypatch: pytest.MonkeyPatch,
-):
+) -> None:
     '''
     Preserve a stream overrun when its error can not be shipped.
 
@@ -108,10 +108,13 @@ def test_overrun_error_send_tolerates_transport_close(
     )
     packed: dict[str, object] = {}
 
+    # Spy on the generated `StreamOverrun` and return a stable wire
+    # `Error`; the real packer adds traceback/relay details unrelated to
+    # this test's secondary transport-close contract.
     def pack_overrun(
         local_err: BaseException,
         cid: str,
-        **kwargs,
+        **kwargs: object,
     ) -> tractor.msg.Error:
         packed['local_err'] = local_err
         packed['cid'] = cid
@@ -275,7 +278,7 @@ async def simple_setup_teardown(
         _state = False
 
 
-async def assert_state(value: bool):
+async def assert_state(value: bool) -> None:
     global _state
     assert _state == value
 
@@ -286,7 +289,7 @@ async def test_cancel_during_context_startup(
     tmp_path: Path,
     start_method: str,
     debug_mode: bool,
-):
+) -> None:
     '''
     Cancel a context after sending `Start` but before its ack.
 
@@ -303,6 +306,7 @@ async def test_cancel_during_context_startup(
     started_path = tmp_path / 'startup_started'
     cancelled_path = tmp_path / 'startup_cancelled'
     start_sent = trio.Event()
+    start_funcs: list[str] = []
     original_send = tractor.Channel.send
 
     async def delay_after_start(
@@ -317,7 +321,11 @@ async def test_cancel_during_context_startup(
             hide_tb=hide_tb,
             send_deadline=send_deadline,
         )
+        # The patched method keeps `Channel.send()`'s broad message
+        # contract. It sees both the requested endpoint `Start` and the
+        # internal `self._cancel_task` startup RPC used for cleanup.
         if isinstance(payload, tractor.msg.Start):
+            start_funcs.append(payload.func)
             if payload.func == 'startup_cancel_target':
                 start_sent.set()
             await trio.sleep_forever()
@@ -333,7 +341,7 @@ async def test_cancel_during_context_startup(
             raise AssertionError('context startup should be cancelled')
 
     async with tractor.open_nursery() as an:
-        actor = tractor.current_actor()
+        actor: Actor = tractor.current_actor()
         portal: tractor.Portal = await an.start_actor(
             'startup_cancel_worker',
             enable_modules=[__name__],
@@ -365,6 +373,10 @@ async def test_cancel_during_context_startup(
             'return_one',
         ) == 1
         assert non_registration_contexts(actor) == contexts_before
+        assert start_funcs == [
+            'startup_cancel_target',
+            '_cancel_task',
+        ]
         await portal.cancel_actor()
 
 
@@ -372,7 +384,7 @@ async def test_cancel_during_context_startup(
 async def test_start_serialization_error_cleans_context(
     start_method: str,
     debug_mode: bool,
-):
+) -> None:
     '''
     Deallocate caller state when `Start` can not be serialized.
 
@@ -385,7 +397,7 @@ async def test_start_serialization_error_cleans_context(
 
     '''
     async with tractor.open_nursery() as an:
-        actor = tractor.current_actor()
+        actor: Actor = tractor.current_actor()
         portal: tractor.Portal = await an.start_actor(
             'serialization_error_worker',
             enable_modules=[__name__],
@@ -414,7 +426,7 @@ async def test_start_serialization_error_cleans_context(
 async def test_start_module_error_cleans_context(
     start_method: str,
     debug_mode: bool,
-):
+) -> None:
     '''
     Deallocate caller state after a remote startup rejection.
 
@@ -427,7 +439,7 @@ async def test_start_module_error_cleans_context(
 
     '''
     async with tractor.open_nursery() as an:
-        actor = tractor.current_actor()
+        actor: Actor = tractor.current_actor()
         portal: tractor.Portal = await an.start_actor(
             'module_error_worker',
         )