Hold the repairs a photographer makes, and say which may share a pass

A spot is a disc, a source offset and four numbers, and it lives beside
`ops` for the reason `masks` and `film` do: the operation trait is
ParamId -> f32, and a list of repairs is neither scalar nor fixed.

Two decisions here are not obvious. The id is derived from the position
rather than counted, because two devices editing offline would each mint
`spot3` for different marks and the sidecar merge would then treat two
repairs as one — from the position, two devices that removed the same
piece of dust agree, and two that removed different ones do not. And
every length is in the frame's isotropic units, not a mixture of those
and shorter-edge fractions: one unit for the radius, the feather and the
offset agrees on a landscape frame and on a portrait one, where a mixture
only agrees on the first.

`rounds` is the arithmetic that keeps a source from reading a
destination. Every spot in one pass reads the photograph as it stood
before that pass, so a spot sourcing from an earlier spot's destination
would copy the mark that spot was removing. Grouping is not a pass per
spot — that is sixty-four dispatches for a case that almost never arises
— it is a new round only when the sources actually collide.

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

core/dr-pipeline/src/graph.rs

@@ -14,6 +14,7 @@ use crate::framing::{CropRect, Framing};
 use crate::mask::MaskStack;
 use crate::operation::{compose_full, ComposedShader, Operation};
 use crate::ops;
+use crate::spot::SpotSet;
 
 /// TRACES: FR-DEV-3a
 /// What one operation offers, as plain data.
@@ -105,6 +106,15 @@ pub struct EditGraph {
     /// that render — because they are one fact, and holding them apart is how
     /// a sidecar comes to name one stock while the shader draws another.
     film: Option<Film>,
+    /// TRACES: FR-DEV-8
+    /// The repairs (`docs/spot-removal.md`).
+    ///
+    /// Apart from `ops` for the third time and the same reason: a spot is not
+    /// a scalar, and a list of them is not a slider. It sits beside the masks
+    /// rather than among them because it is not a mask either — a mask says
+    /// *where* an adjustment applies, and a spot says where a piece of the
+    /// photograph comes from.
+    spots: SpotSet,
 }
 
 /// TRACES: FR-DEV-3f
@@ -148,6 +158,7 @@ impl EditGraph {
             framing: Framing::new(),
             masks: MaskStack::new(),
             film: None,
+            spots: SpotSet::new(),
         }
     }
 
@@ -173,6 +184,16 @@ impl EditGraph {
         graph
     }
 
+    /// TRACES: FR-DEV-8
+    /// The repairs.
+    pub fn spots(&self) -> &SpotSet {
+        &self.spots
+    }
+
+    pub fn spots_mut(&mut self) -> &mut SpotSet {
+        &mut self.spots
+    }
+
     /// The local adjustment stack.
     pub fn masks(&self) -> &MaskStack {
         &self.masks
@@ -402,6 +423,7 @@ impl EditGraph {
         !self.ops.iter().any(|o| o.is_active())
             && !self.framing.edits_image()
             && self.masks.is_neutral()
+            && self.spots.is_neutral()
     }
 
     /// Generate the fused shader for the current state, encoded to sRGB.
@@ -552,6 +574,14 @@ impl EditGraph {
             }
         }
 
+        // TRACES: FR-DEV-8
+        // The repairs belong to the detail stage, because that is where they
+        // run. Moving a spot therefore re-runs the neighbourhood passes and
+        // leaves the fused colour dispatch and the demosaic alone, which is
+        // the difference between a spot that follows the finger and one that
+        // stutters (FR-DEV-3d).
+        detail = self.spots.hash(detail);
+
         crate::Invalidation::new(geometry, colour, detail)
     }
 }