Drop test-local timeouts, +`sync_pause` to dev

In `pyproject.toml`,
- include the `sync_pause` group from `dev`, so dev
  installs ship `greenback` for `pause_from_sync()`.

Comment out per-test `@pytest.mark.timeout(...)`
markers in,
- `tests/devx/test_debugger.py`
- `tests/discovery/test_registrar.py`
- `tests/spawn/test_main_thread_forkserver.py`
- `tests/spawn/test_subint_cancellation.py`
- `tests/test_advanced_streaming.py`
- `tests/test_cancellation.py`

The global cap was already dropped (3c366cac); these
were the leftover per-test caps which now block
interactive `pdb` flows under the new spawn backends.

In `uv.lock`,
- pull `greenback` into the resolved `dev` deps
  (per the `sync_pause` include above).
- catch up the prior `xonsh` editable→PyPI switch
  (from the `pyproject.toml` `tool.uv.sources` edit).

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

(cherry picked from commit b7115fc875)
(factored: dropped spawn-backend-only paths under tests/spawn/)

pyproject.toml

@@ -61,6 +61,7 @@ dev = [
   {include-group = 'devx'},
   {include-group = 'testing'},
   {include-group = 'repl'},
+  {include-group = 'sync_pause'},
 ]
 devx = [
   # `tractor.devx` tooling

tests/devx/conftest.py

@@ -4,6 +4,7 @@
 '''
 from __future__ import annotations
 import platform
+import os
 import signal
 import time
 from typing import (
@@ -90,7 +91,6 @@ def spawn(
         https://docs.python.org/3/using/cmdline.html#using-on-controlling-color
 
         '''
-        import os
         # disable colored tbs
         os.environ['PYTHON_COLORS'] = '0'
         # disable all ANSI color output
@@ -104,7 +104,6 @@ def spawn(
         without requiring per-script CLI plumbing.
 
         '''
-        import os
         os.environ['TRACTOR_SPAWN_METHOD'] = start_method
 
     def set_loglevel():
@@ -116,7 +115,6 @@ def spawn(
         the test harness without per-script edits.
 
         '''
-        import os
         if loglevel:
             os.environ['TRACTOR_LOGLEVEL'] = loglevel
         else:
@@ -176,13 +174,11 @@ def spawn(
         if ptyproc.isalive():
             ptyproc.kill(signal.SIGKILL)
 
-    # Scope our env-var mutations to this single fixture
+    # Scope our env-var mutations to this single fixture invocation
-    # invocation — both `TRACTOR_SPAWN_METHOD` and
+    # — both `TRACTOR_SPAWN_METHOD` and `TRACTOR_LOGLEVEL` are
-    # `TRACTOR_LOGLEVEL` are honored by
+    # honored by `tractor._root.open_root_actor()` so leaking them
-    # `tractor._root.open_root_actor()` so leaking them past
+    # past this test could inadvertently re-route a later in-process
-    # this test could inadvertently re-route a later
+    # tractor test's spawn-backend / loglevel.
-    # in-process tractor test's spawn-backend / loglevel.
-    import os
     os.environ.pop('TRACTOR_SPAWN_METHOD', None)
     os.environ.pop('TRACTOR_LOGLEVEL', None)
 

tests/devx/test_debugger.py

@@ -841,7 +841,7 @@ def test_multi_nested_subactors_error_through_nurseries(
     )
 
 
-@pytest.mark.timeout(15)
+# @pytest.mark.timeout(15)
 @has_nested_actors
 def test_root_nursery_cancels_before_child_releases_tty_lock(
     spawn,

tests/discovery/test_registrar.py

@@ -535,13 +535,13 @@ async def kill_transport(
 # At timeout the plugin hard-kills the pytest process — that's
 # the intended behavior here; the alternative is an unattended
 # suite run that never returns.
-@pytest.mark.timeout(
+# @pytest.mark.timeout(
-    30,
+#     30,
-    # NOTE should be a 2.1s happy path.
+#     # NOTE should be a 2.1s happy path.
-    # XXX for `main_thread_forkserver` this is SUPER SENSITIVE
+#     # XXX for `main_thread_forkserver` this is SUPER SENSITIVE
-    # so keep it higher to avoid flaky runs..
+#     # so keep it higher to avoid flaky runs..
-    method='thread',
+#     method='thread',
-)
+# )
 @pytest.mark.skipon_spawn_backend(
     'subint',
     # 'main_thread_forkserver',

tests/test_advanced_streaming.py

@@ -430,10 +430,10 @@ async def inf_streamer(
     print('streamer exited .open_streamer() block')
 
 
-@pytest.mark.timeout(
+# @pytest.mark.timeout(
-    6,
+#     6,
-    method='signal',
+#     method='signal',
-)
+# )
 def test_local_task_fanout_from_stream(
     reg_addr: tuple,
     debug_mode: bool,

tests/test_cancellation.py

@@ -458,10 +458,10 @@ async def spawn_and_error(
 # `test_nested_multierrors`. See
 # `ai/conc-anal/subint_forkserver_test_cancellation_leak_issue.md`
 # / #449 for the post-mortem.
-@pytest.mark.timeout(
+# @pytest.mark.timeout(
-    10,
+#     10,
-    method='thread',
+#     method='thread',
-)
+# )
 @tractor_test
 async def test_nested_multierrors(
     reg_addr: tuple,