home: fix nav active-section at page bottom + exact progress bar; add blog tags to Writing

- Nav underline highlighted the wrong section at the bottom (the short last
  section never crossed the threshold) — force the last section when scrolled
  to the bottom so Contact lights up instead of Skills
- Scroll-progress bar: compute progress from scrollY/maxScroll so it spans a
  true 0→1 (Motion's default topped out ~0.89 at the bottom)
- Writing section: add blog tag chips linking to /blog/tags/<tag>/

src/scripts/anim.ts

@@ -72,9 +72,15 @@ function run(): void {
    *    bottom (the progress=1 boundary); the callback maps 0→1 cleanly both ways. */
   const bar = document.querySelector<HTMLElement>(".scroll-progress");
   if (bar) {
-    scroll((progress: number) => {
-      bar.style.transform = `scaleX(${progress})`;
-    });
+    // Compute progress straight from scroll position so it reliably spans 0→1
+    // (Motion's default scroll progress topped out ~0.89 at the true bottom).
+    const setBar = (): void => {
+      const max = document.documentElement.scrollHeight - window.innerHeight;
+      const p = max > 0 ? Math.min(1, Math.max(0, window.scrollY / max)) : 0;
+      bar.style.transform = `scaleX(${p})`;
+    };
+    scroll(setBar);
+    setBar();
   }
 
   /* 5. Nav — animated active-section underline + tactile hover. */
@@ -112,11 +118,18 @@ function initNav(): void {
   );
   if (sectioned.length) {
     const setActive = (): void => {
-      const line = window.innerHeight * 0.4; // section crossing the upper area is "active"
+      const vh = window.innerHeight;
+      const ref = vh * 0.45; // the section whose top has passed this reading line is "active"
       let current: HTMLAnchorElement | null = null;
       for (const a of sectioned) {
         const sec = document.getElementById(a.dataset.navId as string);
-        if (sec && sec.getBoundingClientRect().top <= line) current = a;
+        if (sec && sec.getBoundingClientRect().top <= ref) current = a;
+      }
+      // At the very bottom the last (often short) section may never push its top
+      // above the ref line — force it, so Contact lights up at the end instead of
+      // the highlight getting stuck on the previous section (Skills).
+      if (window.scrollY + vh >= document.documentElement.scrollHeight - 4) {
+        current = sectioned[sectioned.length - 1];
       }
       if (current !== active) {
         if (active) under(active, false);