wip(assembler): round L1 -- Linux baseline on abyss: Linux world identical to Windows

Headless Linux benchmark/hash tool (Clang 19 / GCC 14) sharing the viewer's plan builder and
streaming pipeline (moved verbatim into StreamBenchmarkPipeline.h / WorldAssemblyPrototype.h).
Owner Round17 view: density/mesh/payload/topology hashes equal the Windows S13 reference at
W1/W8/W12 (Clang, 3 runs each) and W8 (GCC), with -ffp-contract=off. No output change.
Baseline (i9-12900H, CPUs 0-11, powersave/balance_performance): whole view W8 3.562 s median,
W12 3.512 s, W1 16.555 s; peak RSS < 605 MiB.
Review: the default-stack crash is 17.3 MiB of static TLS per thread (glibc puts it in the
thread stack; HeightfieldColumnCache 6.8 MB), not recursion -- open, after S14.
MSVC compile of the viewer refactor not verified (no MSVC here).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Standalone/Research/WorldAssemblerM3/Linux1/MeasureProcess.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+"""Run one child and report its wait4 peak RSS without /usr/bin/time."""
+import os
+import resource
+import sys
+import time
+
+if len(sys.argv) < 2:
+    raise SystemExit("usage: MeasureProcess.py executable [arguments ...]")
+
+address_limit, _ = resource.getrlimit(resource.RLIMIT_AS)
+stack_limit, _ = resource.getrlimit(resource.RLIMIT_STACK)
+if address_limit in (resource.RLIM_INFINITY, -1) or address_limit > 6 * 1024**3:
+    raise SystemExit("run under prlimit --as=6442450944")
+if stack_limit in (resource.RLIM_INFINITY, -1) or stack_limit < 64 * 1024**2:
+    raise SystemExit("run under prlimit --stack=67108864:67108864")
+if not os.sched_getaffinity(0).issubset(set(range(12))):
+    raise SystemExit("run under taskset -c 0-11")
+print(f"[ProcessLimits] address_limit={address_limit} stack_limit={stack_limit} affinity={sorted(os.sched_getaffinity(0))}", flush=True)
+
+started = time.monotonic()
+pid = os.fork()
+if pid == 0:
+    try:
+        os.execvp(sys.argv[1], sys.argv[1:])
+    except OSError as error:
+        print(f"MeasureProcess: exec failed: {error}", file=sys.stderr, flush=True)
+        os._exit(127)
+
+_, status, usage = os.wait4(pid, 0)
+wall = time.monotonic() - started
+exit_code = os.waitstatus_to_exitcode(status)
+print(f"[ProcessResources] exit_code={exit_code} wall_s={wall:.6f} peak_rss_kib={usage.ru_maxrss}", flush=True)
+raise SystemExit(exit_code)