docs: the verification builds xlings from its main branch

The ninth section builds the largest consumer of mcpp, xlings, from its main
branch with the release under test and runs the program. Locally against the
branch: 9 passed.

Author: speak-agent

.agents/docs/2026-09-30-build-wall-time-verify.sh

@@ -146,6 +146,15 @@ if MCPP_VERBOSE=1 "$MCPP" build > s7.log 2>&1 && grep -q 'build/stage: plan scan
     pass "7 CHANGE: planning states its phases under build/stage"
 else fail "7 CHANGE: the planning phase timers" s7.log; fi
 
+# ── 8. the largest consumer: xlings builds from its main branch ────────────
+rm -rf "$W/s8"; mkdir -p "$W/s8"; cd "$W/s8"
+if git clone -q --depth 1 https://github.com/openxlings/xlings.git xlings > s8-clone.log 2>&1; then
+    cd xlings
+    if "$MCPP" build > ../s8.log 2>&1 && "$(bin_of target xlings)" --version 2>/dev/null | grep -q '^xlings '; then
+        pass "8 xlings builds from its main branch and runs: $(grep -a 'Finished' ../s8.log | tail -1 | sed 's/\x1b\[[0-9;]*m//g; s/^ *//')"
+    else fail "8 xlings from its main branch" ../s8.log; fi
+else skip "8 xlings could not be cloned"; fi
+
 echo
 echo "RESULT: $passes passed, $fails failed, $skips skipped (mcpp $VER)"
 [ "$fails" -eq 0 ]