chain block click: anchored zoom drill-down, entry mode at max zoom

wwwroot/app.js

@@ -304,7 +304,47 @@ function renderChainBlocks(chains) {
       </div>
     `;
     block.querySelector('.block-header').addEventListener('click', () => {
-      openModal(null, null, c.chainId);
+      if (entryMode) {
+        openModal(null, null, c.chainId);
+      } else if (zoomIndex >= ZOOM_LEVELS.length - 1) {
+        // Already at max zoom (1 Tag) - enter entry mode for the bucket containing this chain
+        const chainMid = new Date((new Date(c.first).getTime() + new Date(c.last).getTime()) / 2);
+        const totalMinutes = (viewTo - viewFrom) / 60000;
+        const bucketMinutes = Math.max(1, Math.round(totalMinutes / BAR_COUNT));
+        const bucketMs = bucketMinutes * 60000;
+        const elapsed = chainMid - viewFrom;
+        const bucketIndex = Math.floor(elapsed / bucketMs);
+        const bucketStart = new Date(viewFrom.getTime() + bucketIndex * bucketMs);
+        const bucketEnd = new Date(bucketStart.getTime() + bucketMs);
+        zoomStack.push({ from: new Date(viewFrom), to: new Date(viewTo), zoom: zoomIndex, entry: false });
+        viewFrom = bucketStart;
+        viewTo = bucketEnd;
+        entryMode = true;
+        loadView();
+      } else {
+        const chainMid = new Date((new Date(c.first).getTime() + new Date(c.last).getTime()) / 2);
+        zoomStack.push({ from: new Date(viewFrom), to: new Date(viewTo), zoom: zoomIndex, entry: false });
+        const nextZoom = Math.min(zoomIndex + 1, ZOOM_LEVELS.length - 1);
+        const nextLevel = ZOOM_LEVELS[nextZoom];
+
+        if (nextLevel.weeks) {
+          const anchor = getLastAnchor(chainMid);
+          viewFrom = anchor;
+          viewTo = new Date(anchor.getTime() + nextLevel.weeks * 7 * 86400000);
+        } else {
+          // Day slots within current week
+          const weekStart = getLastAnchor(chainMid);
+          const slotMs = nextLevel.days * 86400000;
+          const elapsed = chainMid - weekStart;
+          const slotIndex = Math.floor(elapsed / slotMs);
+          viewFrom = new Date(weekStart.getTime() + slotIndex * slotMs);
+          viewTo = new Date(viewFrom.getTime() + slotMs);
+        }
+
+        zoomIndex = nextZoom;
+        entryMode = false;
+        loadView();
+      }
     });
     container.appendChild(block);
   });