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/library.slint

@@ -1215,7 +1215,15 @@ export component LibraryGrid inherits Rectangle {
     // also why there is no badge position to compute here any more.
     /// Modifier state at press time, so Rust can decide replace / add / extend
     /// without the .slint file encoding the selection policy.
-    callback cell-pressed(int, bool, bool);
+    ///
+    /// The last argument is **whether a finger did it**, and it is here because
+    /// a finger and a pointer need different rules about what counts as a tap.
+    /// A mouse click is over in tens of milliseconds and means it; a hand
+    /// brushing a tablet on its way somewhere else produces exactly the same
+    /// press-and-release, and used to land the user in develop. Rust holds the
+    /// rule (`collections_ui::TAP_MIN_MS`) beside the hold timer it has to sit
+    /// between — this file only reports which kind of contact it was.
+    callback cell-pressed(int, bool, bool, bool);
     /// TRACES: FR-UI-2 | FR-UI-4
     /// The press on a cell ended — lifted, or taken away by the Flickable when
     /// the finger travelled. Cancels the long-press timer that would otherwise
@@ -3011,6 +3019,10 @@ export component LibraryGrid inherits Rectangle {
                                         i,
                                         ev.modifiers.control || root.select-mode,
                                         ev.modifiers.shift || root.ranging,
+                                        // Finger id 0 is the mouse — the same
+                                        // convention the pinch arbitration a
+                                        // few lines up already relies on.
+                                        ev.touch-finger-id != 0,
                                     );
                                     // One shot. The range was between two taps
                                     // and the second has landed; left armed, it