Tell a tap on a photograph from a hand going past

A brush across the grid opened whichever photograph was under it. Travel
was already answered — the Flickable claims the pointer and the press is
cancelled — but a contact that neither travels nor lasts reaches a
TouchArea as an ordinary press and release, and it was landing the user
in develop.

So a finger now has to stay down for `TAP_MIN_MS` before letting go
counts as opening anything. That is the floor under a tap where the 450 ms
`HOLD_DELAY_MS` is the ceiling: below is a graze, between is a tap, above
is a hold that starts a selection. One scale, three gestures.

Only a finger is held to it. A mouse click is a discrete decision made by
a button and is routinely over in thirty milliseconds, so `cell-pressed`
now reports whether a finger did it — the same finger-id convention the
pinch arbitration beside it already uses — and the dwell applies to touch
alone.

A graze still *selects* the cell it landed on, because the press already
did that. That is the right failure mode: something visible and
reversible rather than a silent nothing, and rather than develop.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/dr-ui/ui/app.slint

@@ -557,7 +557,7 @@ export component AppWindow inherits Window {
     callback library-drag-finished();
     in property <int> library-selected-count: 0;
 
-    callback library-cell-pressed(int, bool, bool);
+    callback library-cell-pressed(int, bool, bool, bool);
     callback library-remove-from-collection();
 
     // The keyboard cursor: where the arrows are in the library, as an image
@@ -1467,8 +1467,8 @@ in property <bool> panel-visible: true;
                     open-settings() => { root.settings-open(); }
                     open-people() => { root.identity-open(); }
 
-                    cell-pressed(i, ctrl, shift) => {
-                        root.library-cell-pressed(i, ctrl, shift);
+                    cell-pressed(i, ctrl, shift, touch) => {
+                        root.library-cell-pressed(i, ctrl, shift, touch);
                     }
                     cell-press-ended() => { root.library-cell-press-ended(); }
                     cell-double-clicked(i) => { root.library-cell-double-clicked(i); }