Replace the instant-jump swipe with a live drag on touch: the current tab
content translates with the finger in real time (translateX driven by
touchmove), a peek chip at the edge shows the destination tab, and on
release the sheet animates to the next tab or snaps back. Horizontal vs
vertical travel is decided after 12px so normal page scrolling is
untouched; touch-action:pan-y keeps horizontal gestures JS-owned. Radar
still pans its map instead of switching tabs.
Touch swipe on the content area moves between tabs (left = next, right =
previous), gated to non-radar views so map pan gestures keep working.
Vertical scroll with |dx|<|dy| is untouched; 60px horizontal threshold.
- New src/lib/router.js: parseHash/ viewToHash for the 5 tab views, with a
default fallback for empty/unknown hashes.
- App.svelte: initialize viewMode from location.hash, setView() updates both
state and the URL hash, and a guarded hashchange listener syncs back/forward
and manual URL edits. All tab onclicks route through setView().
- Tests for parse/viewToHash round-trips and fallback. 76 total pass.
