profile: per-term legacy FI/TN sample profiler (L76); passage/support is ~75% of field time

Opt-in at build time (VOXELFORGE_PROFILE_LEGACY_TERMS=1; compiled out by default, ~2% when on).
Per legacy sample: passage/support composer ~1.05 us vs primitive scan ~0.19 us, boundary
band ~0.06 us, noise ~0.01 us. Resolved-passage constants are cached at field binding
(arithmetic order unchanged); whole-view effect within noise. Per-tile hashes identical to L75
in all 24 compiler x worker x view comparisons; fast tier PASS; Linux UE host builds.
R40 researcher notes attached.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/BuildLinux.sh

@@ -83,6 +83,9 @@ FLAGS+=("${LINK_FLAGS[@]}")
 if [[ "$FP_CONTRACT" != "default" ]]; then
     FLAGS+=("-ffp-contract=$FP_CONTRACT")
 fi
+if [[ "${VOXELFORGE_PROFILE_LEGACY_TERMS:-0}" == "1" ]]; then
+    FLAGS+=(-DVF_L76_PROFILE_LEGACY_TERMS=1)
+fi
 if [[ "$($COMPILER --version | head -n 1)" == *clang* ]]; then
     FLAGS+=(-Wno-c++11-narrowing)
 else