Clarify diff layout, geometry, and bounds naming

AGENTS.md

@@ -57,6 +57,13 @@ CLI input
 - Add inline comments for intent, invariants, or tricky behavior that would not be obvious to a fresh reader.
 - Skip comments that only narrate what the code already says.
 
+## naming
+
+- Prefer names that match the role the code plays in the product and architecture.
+- Use `layout` for structural placement or arrangement data.
+- Use `geometry` for aggregate spatial data used by rendering, scrolling, or interaction.
+- Use `bounds` for one concrete visible extent within a larger structure.
+
 ## review behavior
 
 - Default behavior is a multi-file review stream in sidebar order.

benchmarks/large-stream-profile.ts

@@ -3,7 +3,7 @@
 import { performance } from "perf_hooks";
 import { buildSplitRows } from "../src/ui/diff/pierre";
 import { buildReviewRenderPlan } from "../src/ui/diff/reviewRenderPlan";
-import { measureDiffSectionMetrics } from "../src/ui/lib/sectionHeights";
+import { measureDiffSectionGeometry } from "../src/ui/lib/diffSectionGeometry";
 import { resolveTheme } from "../src/ui/themes";
 import {
   createLargeSplitStreamFiles,
@@ -30,9 +30,9 @@ function measureMs(run: () => void) {
   return performance.now() - start;
 }
 
-const sectionMetricsMs = measureMs(() => {
+const sectionGeometryMs = measureMs(() => {
   windowedFiles.forEach((file) => {
-    measureDiffSectionMetrics(file, "split", true, theme);
+    measureDiffSectionGeometry(file, "split", true, theme);
   });
 });
 
@@ -56,7 +56,7 @@ const noteReviewPlanMs = measureMs(() => {
   });
 });
 
-console.log(`METRIC section_metrics_ms=${sectionMetricsMs.toFixed(2)}`);
+console.log(`METRIC section_geometry_ms=${sectionGeometryMs.toFixed(2)}`);
 console.log(`METRIC split_rows_ms=${splitRowsMs.toFixed(2)}`);
 console.log(`METRIC note_review_plan_ms=${noteReviewPlanMs.toFixed(2)}`);
 console.log(`METRIC split_rows=${windowedRows}`);