fix(workspaces): mobile (tall) grid can't scroll — root height collapse + touch capture

Two blockers for scrolling the tall grid on a phone:

1. HomeTileGrid's root was `flex-1` inside a BLOCK parent (the workspace
   region), so flex-1 did nothing and the root sized to its content; the
   scroller's `h-full` collapsed to auto and overflow-y-auto never engaged —
   extra tiles were clipped by the shell's `overflow-hidden` with no way to
   scroll. The root is now `h-full`, so the scroller gets a definite height
   and tall mode scrolls (wide mode was unaffected: horizontal overflow
   scrolls regardless of container height).

2. `setPointerCapture` was called for TOUCH pointers at pointerdown, which
   can suppress native panning in WebKit. Touch now skips explicit capture:
   the browser's implicit capture already retargets the press, and after the
   long-press lift the moved events bubble up to the grid container where the
   handlers live — scroll gestures keep working and touch drags are intact.

Verification: svelte-check 0 errors/0 warnings; vitest 1694/1694; build ok.
Needs a human on a real phone: swipe the tall grid when tiles overflow —
it must scroll; long-press-and-drag a tile must still reorder.

0 files changed, 0 insertions, 0 deletions