Fix season browser focus: land on first episode on down, ignore parked-cursor hover

- Add data-nav-entry-col-from-above so moving down from the season
  selector always focuses the first episode instead of the tile
  visually closest to the selected season poster; moving back up
  still returns to the current season.
- Require recent real mouse movement before treating mouseover as
  mouse intent: scroll/re-render under a stationary cursor no longer
  activates mouse mode, so sideways season browsing no longer loses
  focus to the episode tile under the parked pointer.

frontend/src/components/SeriesFullView.vue

@@ -548,6 +548,9 @@ function getEpisodeNavAttrs(seasonIndex: number, episodeIndex: number) {
     ...navAttrs(coords.row, coords.col),
     "data-season-index": seasonIndex,
     "data-episode-index": episodeIndex,
+    // Entering the episode grid from above (the season selector) always
+    // lands on the first episode instead of the visually closest tile.
+    ...(episodeIndex === 0 ? { "data-nav-entry-col-from-above": "0" } : {}),
   }
 }
 

frontend/src/composables/useInputModality.ts

@@ -6,6 +6,7 @@ type InputModality = "mouse" | "keyboard" | "gamepad"
 const MOUSE_IDLE_MS = 1400
 const MOUSE_INTENT_DISTANCE_PX = 28
 const MOUSE_INTENT_WINDOW_MS = 700
+const MOUSE_OVER_INTENT_RECENCY_MS = 500
 const MOUSE_INTENT_SELECTOR = [
   "[data-nav-focusable]",
   "button",
@@ -28,6 +29,7 @@ let mouseIdleTimer: number | null = null
 let pointerVisible = false
 let mouseTravelPx = 0
 let lastMouseMoveAt = 0
+let lastAnyMouseMoveAt = 0
 
 function clearMouseIdleTimer() {
   if (mouseIdleTimer !== null) {
@@ -95,6 +97,7 @@ function registerMouseIntentTravel(event: MouseEvent): boolean {
 function handleMouseMove(event: MouseEvent) {
   reportUserActivity()
   showPointerFromMotion()
+  lastAnyMouseMoveAt = performance.now()
 
   if (modality === "mouse") {
     applyInputState(true)
@@ -111,6 +114,13 @@ function handleMouseOver(event: MouseEvent) {
   if (modality === "mouse") return
   if (!isMouseIntentTarget(event.target)) return
 
+  // Browsers fire mouseover/mouseenter when scrolling or re-rendering moves
+  // content under a stationary cursor (e.g. sideways season browsing while
+  // the pointer happens to rest over the episode grid). Without recent real
+  // pointer motion this is not mouse intent — activating mouse input here
+  // would let hover handlers steal keyboard/gamepad focus.
+  if (performance.now() - lastAnyMouseMoveAt > MOUSE_OVER_INTENT_RECENCY_MS) return
+
   // Entering an interactive target indicates likely mouse intent.
   activateMouseInput()
 }

frontend/src/composables/useKeyboardNavigation.ts

@@ -36,6 +36,10 @@ const FOCUSABLE_ATTR = "data-nav-focusable"
 const ROW_ATTR = "data-nav-row"
 const COL_ATTR = "data-nav-col"
 const ENTRY_COL_ATTR = "data-nav-entry-col"
+// Like ENTRY_COL_ATTR, but only applies when entering the row from above
+// (ArrowDown). Lets a row declare a fixed landing column for downward entry
+// without hijacking upward or horizontal moves.
+const ENTRY_COL_FROM_ABOVE_ATTR = "data-nav-entry-col-from-above"
 const SYNC_SCROLL_ROW_ATTR = "data-sync-scroll-row"
 const SYNC_SCROLL_GROUP_ATTR = "data-sync-scroll-group"
 const DEFAULT_SYNC_SCROLL_GROUP = "browse"
@@ -672,8 +676,23 @@ function findNextElement(
       desiredCol.value = currentCol
     }
 
-    const entryTarget = findElementAt(targetRow, targetCol, true)
     const targetRowElements = byRow.get(targetRow) ?? []
+
+    if (direction === "down") {
+      for (const el of targetRowElements) {
+        const fromAboveCol = el.element.getAttribute(ENTRY_COL_FROM_ABOVE_ATTR)
+        if (fromAboveCol === null) continue
+        const fromAboveTarget = targetRowElements.find(
+          (e) => e.col === parseInt(fromAboveCol, 10),
+        )
+        if (fromAboveTarget) {
+          desiredCol.value = fromAboveTarget.col
+          return fromAboveTarget.element
+        }
+      }
+    }
+
+    const entryTarget = findElementAt(targetRow, targetCol, true)
     const hasEntryOverride = targetRowElements.some((el) => el.element.hasAttribute(ENTRY_COL_ATTR))
     if (hasEntryOverride) {
       return entryTarget?.element || null