Fix uds `get_random` reaper-regex break (+2 nits)

Copilot's 2nd-pass review (PR #468) caught a regression I landed in
the uds fix: `UDSAddress.get_random()` put the per-call token AFTER
`@{pid}` (`no_runtime_*@{pid}.{token}.sock`), which breaks the
`tractor._testing._reap` matcher
`^(?P<name>.+)@(?P<pid>\d+)\.sock$` — so no-runtime orphan socks
stopped matching and never got reaped/attributed. Move the token
INTO the name (`{prefix}.{token}@{pid}.sock`) so the canonical
`@{pid}.sock` suffix stays intact for both that regex and the
`spawn._reap` reconstruction; also bump the token to 8 hex chars.

Also two robustness nits from the same review,
- `tests.conftest._measure_sustained_headroom()`: guard `frac <= 0`
  before `1./frac` — a 0/parked-core freq read would
  `ZeroDivisionError`, get swallowed by the broad `except` into a
  1.0 (no-throttle), defeating the probe on the exact broken box it
  should flag; read 0 as max throttle.
- `scripts/cpu-perf-check`: mark the burn procs `daemon=True` and
  wrap sampling in `try/finally` so a Ctrl-C / error reaps them
  instead of leaving stray CPU hogs.

Regressed-by: 09c50f49 (uds no-runtime token placed after `@pid`)
Found-via: Copilot review #4595803812 (`_testing._reap` regex)
Review: PR #468 (Copilot)
https://github.com/goodboy/tractor/pull/468#pullrequestreview-4595803812

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

scripts/cpu-perf-check

@@ -112,21 +112,28 @@ def main(
     print(f'\n=== sustained {ncpu}-core load ({secs:.0f}s) — the real test ===')
     stop: float = time.perf_counter() + secs
     procs = [
-        mp.Process(target=_burn, args=(stop,))
+        mp.Process(target=_burn, args=(stop,), daemon=True)
         for _ in range(ncpu)
     ]
     for p in procs:
         p.start()
 
-    # skip the initial ~0.6s ramp, then sample steady-state
+    # skip the initial ~0.6s ramp, then sample steady-state.
+    # `try/finally` so a Ctrl-C / sampling error still reaps the
+    # burners instead of leaving stray CPU hogs (daemon=True is the
+    # backstop should we exit abnormally before the join).
     samples: list[int] = []
-    time.sleep(0.6)
-    while time.perf_counter() < stop - 0.2:
-        if (fr := _cur_freqs_mhz()):
-            samples.append(sum(fr) // len(fr))
-        time.sleep(0.3)
-    for p in procs:
-        p.join()
+    try:
+        time.sleep(0.6)
+        while time.perf_counter() < stop - 0.2:
+            if (fr := _cur_freqs_mhz()):
+                samples.append(sum(fr) // len(fr))
+            time.sleep(0.3)
+    finally:
+        for p in procs:
+            p.terminate()
+        for p in procs:
+            p.join()
 
     if not (samples and pkg_max):
         print('  could not sample cur freq — assume OK')

tests/conftest.py

@@ -236,6 +236,12 @@ def _measure_sustained_headroom(
         # under-shoots and still trips the marginal cases).
         if frac >= throttle_gate:
             return 1.
+        # a 0/parked-core freq read would `ZeroDivisionError` the
+        # inverse below — silently swallowed by the outer `except`
+        # into a 1.0 (no-throttle), defeating the probe on exactly
+        # the broken box it should flag; read 0 as max throttle.
+        if frac <= 0:
+            return max_headroom
         return min(max_headroom, 1. / frac)
 
     except Exception:

tractor/ipc/_uds.py

@@ -205,16 +205,18 @@ class UDSAddress(
             else:
                 prefix: str = 'no_runtime_actor'
 
-            # XXX, no live actor -> no `Aid` to key off, so append a
-            # per-CALL token: w/o a runtime the sockname is otherwise
-            # a pure fn of `(prefix, pid)`, so two `get_random()`
-            # calls in one proc alias to the SAME sockpath and the
-            # 2nd `.bind()` trips `EADDRINUSE`. The token makes each
-            # call a distinct file. Safe vs `._reap` cleanup which
-            # only reconstructs the runtime `{name}@{pid}` convention
-            # (above), never these `no_runtime_*` socks.
-            token: str = uuid4().hex[:6]
-            sockname: str = f'{prefix}@{pid}.{token}'
+            # XXX, no live actor -> no `Aid` to key off, so mix a
+            # per-CALL token into the NAME part for uniqueness:
+            # w/o a runtime the sockname is otherwise a pure fn of
+            # `(prefix, pid)`, so two `get_random()` calls in one
+            # proc alias to the SAME sockpath and the 2nd `.bind()`
+            # trips `EADDRINUSE`. Token goes BEFORE `@{pid}` so the
+            # canonical `...@{pid}.sock` suffix stays intact for the
+            # reapers keyed off it: `._testing._reap`'s
+            # `(?P<name>.+)@(?P<pid>\d+)\.sock` regex, and the
+            # `spawn._reap` `{name}@{pid}.sock` reconstruction.
+            token: str = uuid4().hex[:8]
+            sockname: str = f'{prefix}.{token}@{pid}'
 
         sockpath: Path = Path(f'{sockname}.sock')
         return UDSAddress(