Use `cpu_perf_headroom()` at remaining deadlines

Finish TODO #2 from PR #468: the last raw `cpu_scaling_factor()`
call-sites still used the static-only check (blind to the
sustained-load power-cap). Point them at the `cpu_perf_headroom()`
SUPERSET — it calls `cpu_scaling_factor()` internally + the
session-cached throttle probe, so it's always >= the old factor
(never LESS headroom, so CI stays green).

Migrated,
- `test_spawning`: the `fail_after(1 * ...)` smoke deadline
  (#465-added).
- `test_inter_peer_cancellation`: `this_fast` budget.
- `test_docs_examples`: example-run `timeout`.
- `test_resource_cache`: fan-out `timeout`.

`test_cancellation` already used `cpu_perf_headroom()`; only its
explanatory comments still name the static helper.

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

tests/test_docs_examples.py

@@ -160,7 +160,7 @@ def test_example(
             'root-causing. Passes on Linux.'
         )
 
-    from .conftest import cpu_scaling_factor
+    from .conftest import cpu_perf_headroom
 
     timeout: float = (
         60
@@ -168,8 +168,9 @@ def test_example(
         else 16
     )
 
-    # add latency headroom for CPU freq scaling (auto-cpufreq et al.)
-    headroom: float = cpu_scaling_factor()
+    # add latency headroom for CPU freq scaling/throttle
+    # (auto-cpufreq et al.)
+    headroom: float = cpu_perf_headroom()
     if headroom != 1.:
         timeout *= headroom
 

tests/test_inter_peer_cancellation.py

@@ -24,7 +24,7 @@ from tractor._testing import (
     expect_ctxc,
 )
 
-from .conftest import cpu_scaling_factor
+from .conftest import cpu_perf_headroom
 
 pytestmark = [
     pytest.mark.skipon_spawn_backend(
@@ -1280,12 +1280,12 @@ def test_peer_spawns_and_cancels_service_subactor(
 
 
     async def _main():
-        headroom: float = cpu_scaling_factor()
+        headroom: float = cpu_perf_headroom()
         this_fast_on_linux: float = 3
         this_fast = this_fast_on_linux * headroom
         if headroom != 1.:
             test_log.warning(
-                f'Adding latency headroom on linux bc CPU scaling,\n'
+                f'Adding latency headroom on linux bc CPU perf scaling/throttle,\n'
                 f'headroom: {headroom}\n'
                 f'this_fast_on_linux: {this_fast_on_linux} -> {this_fast}\n'
             )

tests/test_resource_cache.py

@@ -213,12 +213,12 @@ def test_open_local_sub_to_stream(
     N local tasks using `trionics.maybe_open_context()`.
 
     '''
-    from .conftest import cpu_scaling_factor
+    from .conftest import cpu_perf_headroom
     timeout: float = (
         4
         if not platform.system() == "Windows"
         else 10
-    ) * cpu_scaling_factor()
+    ) * cpu_perf_headroom()
 
     if debug_mode:
         timeout = 999

tests/test_spawning.py

@@ -153,9 +153,9 @@ async def test_most_beautiful_word(
     # actor spawn + IPC round-trip is comfortably sub-second on a
     # warm box, but slow/noisy CI runners (esp. macOS) blow a flat
     # 1s deadline. Scale for CI/CPU-throttle headroom — `== 1s`
-    # locally where `cpu_scaling_factor()` is `1.0`.
-    from .conftest import cpu_scaling_factor
-    with trio.fail_after(1 * cpu_scaling_factor()):
+    # locally where `cpu_perf_headroom()` is `1.0`.
+    from .conftest import cpu_perf_headroom
+    with trio.fail_after(1 * cpu_perf_headroom()):
         async with tractor.open_nursery(
             debug_mode=debug_mode,
         ) as an: