test/run: phase-2 byte-id gates run parallel; rule-14 NNN constraint retired (test-perf T3b)

With intermediates following the output stem, concurrent wwstage-driver
builds no longer share paths - 950/990-997 join the xargs -P group.
Measured: 202.7s -> 153.8s full-test wall (x2 runs race-clean); the
serial tail (57.7% of wall) is gone, remainder is CPU-bound. CLAUDE.md
rule 14 documents the new reality: NNN range no longer a correctness
constraint, still keys phase membership / skip set / cache set.

test/run

@@ -132,12 +132,12 @@ fi
 # so the collector can report wall shares onto ken's three poles.
 run_start=$(date +%s.%N)
 
-# Phase 2 runs the wwstage byte-id gates (990-997) + 950_selfcheck.
-# ww_ww writes intermediates next to every traversed source (task #15),
-# so 991/992/994's reads of selfhost/cmd/<tool>/main.{s,o,combined.ww}
-# race against any concurrent driver-using test that emits a sibling
-# .combined.ww (task #16). Phase 1 stays parallel for unit coverage; the
-# wwstage-driver tests stay out of phase 1 to keep those reads honest.
+# Phase 2 runs the wwstage byte-id / self-compile gates (990-997) +
+# 950_selfcheck. They're kept out of phase 1 only so the heavy 43k
+# self-compiles don't contend with the phase-1 fixture swarm; within
+# phase 2 they all run in parallel (post-T3 each build's intermediates
+# follow its output via `-o`/temp, so no member writes a path another
+# reads — see the phase-2 block below).
 for t in test/wcc/*.c; do
 	[ -f "$t" ] || continue
 	case ${t##*/} in
@@ -170,34 +170,22 @@ if [ "${UNIT:-0}" != "1" ]; then
 	done
 	else
 	p2par_start=$(date +%s.%N)
-	# Phase 2 is partitioned (#3): the pure-reader byte-id gates run in
-	# parallel; the source-tree writers run in a serial tail afterward.
-	#
-	# PARALLEL GROUP — 990/991/992/994/996/997. Each reads only committed
-	# or make-all-produced files and writes only /tmp or a disjoint tracked
-	# stem (990→out smoke.*, 996→examples/mandelbrot/*, 997→/tmp fixture
-	# copy). No group member writes a stem another member reads (per-gate FS
-	# footprint audited race-free, #3), so they fan out via the same
-	# xargs -P "$JOBS" machinery as phase 1.
+	# Phase 2 — the wwstage byte-id / self-compile gates, all parallel.
+	# Pre-T3 the source-tree writers (993/995/950) ran in a serial tail
+	# because ww_ww wrote intermediates next to every traversed source, so
+	# they raced each other AND the 990/991/992/994 readers. T3 made every
+	# build's .combined.ww/.s/.o follow its OUTPUT (`-o`/per-pid temp): 993
+	# → its dc/dw workdirs, 995 → /tmp/wwsr_<pid>_<tool>, 950 → /tmp only.
+	# No member now writes a stem another reads (the readers see only the
+	# stable make-all regen), so the whole group fans out via xargs -P.
 	for t in test/wcc/990_*.c test/wcc/991_*.c test/wcc/992_*.c \
-	         test/wcc/994_*.c test/wcc/996_*.c test/wcc/997_*.c; do
+	         test/wcc/993_*.c test/wcc/994_*.c test/wcc/995_*.c \
+	         test/wcc/996_*.c test/wcc/997_*.c test/wcc/950_*.c; do
 		[ -f "$t" ] || continue
 		name=${t##*/}; name=${name%.c}
 		printf '%s/%s\0%s\0' "$RESULTS" "$name" "$t"
 	done | xargs -0 -n2 -P "$JOBS" "$0" --one || true
 	p2par_end=$(date +%s.%N)
-
-	p2ser_start=$(date +%s.%N)
-	# SERIAL TAIL — 993/995/950, the only source-tree writers. 993 & 995
-	# both write cmd/wwdump/main.* (995 writes all 5 cmd/*/main.*), so they
-	# run sequentially w.r.t. each other AND after the parallel group, so
-	# the group's readers see stable make-all output, never a torn write.
-	for t in test/wcc/993_*.c test/wcc/995_*.c test/wcc/950_*.c; do
-		[ -f "$t" ] || continue
-		name=${t##*/}; name=${name%.c}
-		"$0" --one "$RESULTS/$name" "$t" || true
-	done
-	p2ser_end=$(date +%s.%N)
 	fi
 
 	# combined.ww freshness gate (#110): 990/995 above unconditionally