iOS inner loop: use per-call unique logarchive path to eliminate sudo rm hang

The previous code shared a single `ioshelper_startup.logarchive` path across
all iterations and bracketed the `sudo log collect` call with `sudo rm -rf`
calls to purge any stale archive (since `log collect` refuses to overwrite
an existing --output path with exit 74). That works when sudo credentials
are cached, but hangs indefinitely in non-TTY background contexts (e.g.,
campaigns started via detached caffeinate, nohup, or any agent runner)
because the sudo password prompt has no terminal to read from.

NOPASSWD is only practical to scope to `/usr/bin/log collect` (per the
existing /etc/sudoers.d/log-collect convention); scoping it to /bin/rm is
broader than most users want.

Switch to a per-call unique logarchive path
`ioshelper_startup_{pid}_{ms}.logarchive`. macOS's tmp reaper cleans /tmp
on its own schedule, so per-iteration archives don't accumulate harmfully.
`log collect` succeeds on the first try every time since the path never
pre-exists. No sudo rm needed.

Validated by a 4-side M365 campaign overnight: 11 cold-startup events per
side across all 4 configs, zero hangs, with the orchestrator running fully
detached from any user TTY.

Author: davidnguyen-tech

src/scenarios/shared/ioshelper.py

@@ -611,19 +611,22 @@ def _measure_device_startup_via_watchdog(self, bundle_id):
                 launch_proc.wait()
 
         # Collect device logs covering the launch window.
-        # Both rm -rf calls use sudo because `sudo log collect` writes the
-        # logarchive owned by root; an unprivileged rm cannot recurse into it
-        # and `log collect` refuses to overwrite an existing --output path
-        # (exit 74), so a stale archive from iteration N would block iteration
-        # N+1 from collecting any logs.
-        logarchive = os.path.join(tempfile.gettempdir(), 'ioshelper_startup.logarchive')
-        self._run_quiet(['sudo', 'rm', '-rf', logarchive])
+        # Use a unique per-call logarchive path so we don't need to delete a
+        # prior root-owned archive (the upstream code uses `sudo rm -rf` to
+        # purge a stale shared path; that requires interactive sudo when
+        # NOPASSWD is scoped only to `log collect`, which hangs background
+        # campaigns). Per-call uniqueness eliminates the need for cleanup
+        # entirely; macOS's tmp cleaner reaps leaked archives.
+        import time as _time
+        logarchive = os.path.join(
+            tempfile.gettempdir(),
+            f'ioshelper_startup_{os.getpid()}_{int(_time.time() * 1000)}.logarchive')
         collect_cmd = ['sudo', 'log', 'collect', '--device',
                        '--start', start_ts, '--output', logarchive]
         RunCommand(collect_cmd, verbose=True).run()
 
         # Parse SpringBoard watchdog events for this bundle ID.
-        # sudo because the logarchive is root-owned (see comment above).
+        # sudo because the logarchive is root-owned (created by sudo log collect).
         show_cmd = ['sudo', 'log', 'show',
                     '--predicate', '(process == "SpringBoard") && (category == "Watchdog")',
                     '--info', '--style', 'ndjson', logarchive]
@@ -673,8 +676,10 @@ def parse_ts(evt):
         getLogger().info("Cold startup: %d ms (Time to Main: %d ms, Time to First Draw: %d ms)",
                          total_ms, time_to_main_ms, time_to_draw_ms)
 
-        # Clean up logarchive (sudo: log collect ran as root, so the tree is root-owned)
-        self._run_quiet(['sudo', 'rm', '-rf', logarchive])
+        # Skip post-iter cleanup: the logarchive uses a unique per-call name so
+        # accumulation isn't a correctness problem. macOS reaps /tmp on a
+        # schedule. Leaving it avoids needing sudo (which hangs background
+        # campaigns when NOPASSWD is scoped only to `log collect`).
 
         return total_ms