wip(assembler): rounds L5+L6 -- Linux far-terrain captures and screen-space gate (world unchanged)

Linux offscreen capture (EGL/GLES pbuffer; llvmpipe in the sandbox) and an opt-in screen-space gate
for LOD>=3 (normal distance projected at each LOD's closest display distance, 1 px at 1440p =
0.61 mrad). The gate rejects the S13 octave-drop and stride-2 controls, fault injections, and a
vertical-vs-screen control. Finding: today's far meshes differ from the field by up to 92 px, and
LOD swaps snap mesa rims by tens of px (p50 0 px), a silhouette effect of plain LOD switching. The
octave cutoff was dropped: nothing qualified, and octaves are a small share of far time. Off-path
cost: reviewer interleaved W12 within noise vs L4 (+0.6% median). Hashes = L4.
Largest far lever measured: column work outside noise, 34% of far worker time (duplicate XY across tiles).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ED33VnqepD4YY6gDAAA832

Standalone/Research/WorldAssemblerM3/Linux5/MeasureProcess.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+import os
+import signal
+import subprocess
+import sys
+import time
+
+if len(sys.argv) < 4 or sys.argv[2] != "--":
+    raise SystemExit("usage: MeasureProcess.py LOG -- COMMAND [ARGS...]")
+
+log_path = sys.argv[1]
+command = sys.argv[3:]
+os.makedirs(os.path.dirname(log_path) or ".", exist_ok=True)
+start = time.monotonic()
+with open(log_path, "wb") as log_file:
+    process = subprocess.Popen(command, stdout=log_file, stderr=subprocess.STDOUT,
+                               start_new_session=True)
+    max_hwm_kib = 0
+    max_rss_kib = 0
+    max_pid = process.pid
+    max_name = ""
+    deadline = start + 1800.0
+    while process.poll() is None:
+        if time.monotonic() >= deadline:
+            os.killpg(process.pid, signal.SIGTERM)
+            try:
+                process.wait(timeout=10)
+            except subprocess.TimeoutExpired:
+                os.killpg(process.pid, signal.SIGKILL)
+                process.wait()
+            print("MONITOR_TIMEOUT_SECONDS=1800", file=log_file, flush=True)
+            break
+        stat_by_pid = {}
+        for entry in os.scandir("/proc"):
+            if not entry.name.isdigit():
+                continue
+            pid = int(entry.name)
+            try:
+                with open(f"/proc/{pid}/stat", "r", encoding="ascii") as stat_file:
+                    fields = stat_file.read().rsplit(")", 1)[1].split()
+                ppid = int(fields[1])
+                stat_by_pid[pid] = ppid
+            except (OSError, ValueError, IndexError):
+                continue
+        descendants = {process.pid}
+        changed = True
+        while changed:
+            changed = False
+            for pid, ppid in stat_by_pid.items():
+                if ppid in descendants and pid not in descendants:
+                    descendants.add(pid)
+                    changed = True
+        for pid in descendants:
+            try:
+                with open(f"/proc/{pid}/status", "r", encoding="ascii") as status_file:
+                    status = status_file.read().splitlines()
+                values = {line.split(":", 1)[0]: line.split(":", 1)[1].strip()
+                          for line in status if ":" in line}
+                hwm = int(values.get("VmHWM", "0 kB").split()[0])
+                rss = int(values.get("VmRSS", "0 kB").split()[0])
+                name = values.get("Name", "")
+            except (OSError, ValueError, IndexError):
+                continue
+            if hwm > max_hwm_kib:
+                max_hwm_kib, max_pid, max_name = hwm, pid, name
+            max_rss_kib = max(max_rss_kib, rss)
+        time.sleep(0.05)
+    result = process.wait()
+    elapsed = time.monotonic() - start
+    for line in (
+        f"MONITOR_EXIT_CODE={result}",
+        f"MONITOR_WALL_SECONDS={elapsed:.3f}",
+        f"MONITOR_PEAK_PROCESS_HWM_KIB={max_hwm_kib}",
+        f"MONITOR_PEAK_PROCESS_PID={max_pid}",
+        f"MONITOR_PEAK_PROCESS_NAME={max_name}",
+        f"MONITOR_MAX_SAMPLED_PROCESS_RSS_KIB={max_rss_kib}",
+    ):
+        log_file.write((line + "\n").encode("utf-8"))
+raise SystemExit(result)
+