UI: drop tab-bar tap highlight; don't slide the first screen on launch

Tab bar: tapping a bottom-tab icon flashed a background — the icon square's
:active press tint plus the default WebKit tap flash, the same pair removed from
the lobby rows. Drop the press tint and set -webkit-tap-highlight-color:
transparent on .tab. The selected-tab highlight (Settings / Comms hubs) stays.

Startup slide: the route pane's in:slideX is local to its {#key} block, so it
plays on that block's own first mount when app.ready flips — the lobby slid in on
launch as if navigated into from another screen. Gate the slide duration to 0 for
the first pane shown after boot (a `started` flag set right after it mounts), so
launch is static while every later route change animates as before.

ui/src/App.svelte

@@ -32,8 +32,9 @@
 
   // Screen transitions: the lobby is the navigation root. Entering a screen from the
   // lobby slides it in from the right (forward); returning to the lobby slides the
-  // screen out to the right and reveals the lobby (back). Transitions are local, so
+  // screen out to the right and reveals the lobby (back). The first pane shown after boot
-  // they do not play on the initial mount, and collapse to nothing under reduce-motion.
+  // does not slide (the `started` gate below), and transitions collapse to nothing under
+  // reduce-motion.
   // Slide direction by route depth: going deeper (lobby → game → chat/check) slides forward,
   // returning to a shallower screen slides back. A plain "lobby is back" rule slid the chat/check
   // back-to-the-game the wrong way. dir is read with the previous depth (the effect updates it
@@ -52,7 +53,15 @@
   const enterSign = $derived(dir === 'forward' ? 1 : -1);
   const leaveSign = $derived(dir === 'forward' ? -1 : 1);
   const routeKey = $derived(router.route.name + (router.route.params.id ?? ''));
-  const animMs = $derived(app.reduceMotion ? 0 : 260);
+  // The first pane shown once the app is ready must not slide: it would look like the app
+  // was navigated into rather than launched. The pane is a local transition inside a {#key}
+  // block, so it plays on that block's own first mount anyway — hold the duration at 0 until
+  // just after that mount (the effect runs post-render), then animate every later change.
+  let started = $state(false);
+  $effect(() => {
+    if (app.ready) started = true;
+  });
+  const animMs = $derived(!started || app.reduceMotion ? 0 : 260);
 
   // slideX slides a pane horizontally by a full width. sign>0 enters from / exits to
   // the right; sign<0 the left. Percentage keeps it viewport-relative without reading

ui/src/components/TabBar.svelte

@@ -34,12 +34,13 @@
     width: 100%;
     user-select: none;
     -webkit-user-select: none;
+    -webkit-tap-highlight-color: transparent; /* no WebKit flash on tap */
   }
   :global(.tab:disabled) {
     opacity: 0.4;
   }
-  /* The icon square hugs the emoji (just a little padding) so it is the press-highlight
+  /* The icon square hugs the emoji (just a little padding) so the badge can sit on its
-     target and the badge can sit on its corner. */
+     corner. */
   :global(.tab .sq) {
     position: relative;
     display: inline-grid;
@@ -50,12 +51,9 @@
     line-height: 1;
     transition: background-color 0.12s;
   }
-  :global(.tab:active:not(:disabled) .sq) {
-    background: var(--surface-2);
-  }
   /* A tab that navigates between peer views (Settings / Comms hubs) stays highlighted
-     while selected: a filled square with an accent underline, distinct from the
+     while selected: a filled square with an accent underline. A tap itself leaves no
-     momentary press tint above. */
+     highlight — there is no press tint, and the WebKit tap flash is disabled on .tab. */
   :global(.tab.active .sq) {
     background: var(--surface-2);
     box-shadow: inset 0 -2px 0 var(--accent);