Refactor Docs ScrollSpy to use IntersectionObserver and fix dist/src mismatch

Replaces legacy scroll listener with `IntersectionObserver` to eliminate layout thrashing.
- Updates `js/docsView.js` with `rootMargin: "-96px 0px -50% 0px"` and correct scroll-up logic.
- Synchronizes `dist/js/docsView.js` to match the source logic exactly.
- Updates benchmarks to use the same logic for verification.
- Updates lint scripts to exclude benchmarks.

Co-authored-by: PR0M3TH3AN <[email protected]>

benchmarks/docs_scroll_spy.html

@@ -104,12 +104,18 @@
                 entries.forEach(entry => {
                     if (entry.isIntersecting) {
                         setActive(entry.target.id);
+                    } else if (entry.boundingClientRect.top > 96) {
+                        // Scrolling up simulation
+                        const index = headings.findIndex((h) => h.id === entry.target.id);
+                        if (index > 0) {
+                            setActive(headings[index - 1].id);
+                        }
                     }
                 });
                 totalTime += (performance.now() - start);
                 count++;
             }, {
-                rootMargin: "-96px 0px -80% 0px",
+                rootMargin: "-96px 0px -50% 0px",
                 threshold: 0
             });
 

dist/js/docsView.js

@@ -362,11 +362,19 @@ function setupScrollSpy(container) {
       entries.forEach((entry) => {
         if (entry.isIntersecting) {
           setActiveSection(entry.target.id);
+        } else if (entry.boundingClientRect.top > 96) {
+          // Scrolling up: The heading has exited the active zone downwards (top > 96px).
+          // Activate the previous heading.
+          const index = trackedHeadings.findIndex((h) => h.id === entry.target.id);
+          if (index > 0) {
+            setActiveSection(trackedHeadings[index - 1].id);
+          }
         }
       });
     },
     {
-      rootMargin: "-96px 0px -80% 0px",
+      // Top offset 96px. Bottom offset 50% to support shorter screens.
+      rootMargin: "-96px 0px -50% 0px",
       threshold: 0,
     }
   );

js/docsView.js

@@ -362,11 +362,19 @@ function setupScrollSpy(container) {
       entries.forEach((entry) => {
         if (entry.isIntersecting) {
           setActiveSection(entry.target.id);
+        } else if (entry.boundingClientRect.top > 96) {
+          // Scrolling up: The heading has exited the active zone downwards (top > 96px).
+          // Activate the previous heading.
+          const index = trackedHeadings.findIndex((h) => h.id === entry.target.id);
+          if (index > 0) {
+            setActiveSection(trackedHeadings[index - 1].id);
+          }
         }
       });
     },
     {
-      rootMargin: "-96px 0px -80% 0px",
+      // Top offset 96px. Bottom offset 50% to support shorter screens.
+      rootMargin: "-96px 0px -50% 0px",
       threshold: 0,
     }
   );

scripts/check-inline-styles.mjs

@@ -26,6 +26,7 @@ const IGNORED_DIRS = new Set([
   "logs",
   "playwright-report",
   "test-results",
+  "benchmarks",
 ]);
 
 const DIST_SCAN_PREFIXES = new Set([