Phase 3.5a: SetImageFillAction + Info-Panel image-fill picker

- SetImageFillAction (core): set/clear `image_fill` on the selected VectorGraph fills,
  with per-fill undo (mirrors SetFillPaintAction). Image takes render priority; clearing
  reveals the colour/gradient underneath.
- Info Panel Shape section: an "Image:" combo listing the document's image assets (+ None)
  for the selected fill(s), showing the current assignment. Assign/clear pushes the action.

This lets an existing shape be given (or cleared of) an image fill, complementing the
import/drop placement. Next: 3.5b — persist image assets in the .beam container.

lightningbeam-ui/lightningbeam-core/src/actions/mod.rs

@@ -40,6 +40,7 @@ pub mod raster_fill;
 pub mod add_raster_keyframe;
 pub mod move_layer;
 pub mod set_fill_paint;
+pub mod set_image_fill;
 
 pub use add_clip_instance::AddClipInstanceAction;
 pub use add_effect::AddEffectAction;
@@ -75,5 +76,6 @@ pub use raster_fill::RasterFillAction;
 pub use add_raster_keyframe::AddRasterKeyframeAction;
 pub use move_layer::MoveLayerAction;
 pub use set_fill_paint::SetFillPaintAction;
+pub use set_image_fill::SetImageFillAction;
 pub use change_bpm::ChangeBpmAction;
 pub use change_fps::ChangeFpsAction;

lightningbeam-ui/lightningbeam-core/src/actions/set_image_fill.rs

@@ -0,0 +1,67 @@
+//! Action that sets or clears the image fill on one or more VectorGraph fills.
+//!
+//! `image_fill` is an asset id the renderer maps onto the fill's bounding box; it
+//! takes priority over colour/gradient. Setting `None` clears it (the colour/gradient
+//! underneath shows again).
+
+use crate::action::Action;
+use crate::document::Document;
+use crate::layer::AnyLayer;
+use crate::vector_graph::FillId;
+use uuid::Uuid;
+
+pub struct SetImageFillAction {
+    layer_id: Uuid,
+    time: f64,
+    fill_ids: Vec<FillId>,
+    /// `Some(asset_id)` to set, `None` to clear.
+    new_image: Option<Uuid>,
+    /// Per-fill previous `image_fill`, for undo.
+    old: Vec<(FillId, Option<Uuid>)>,
+}
+
+impl SetImageFillAction {
+    pub fn new(layer_id: Uuid, time: f64, fill_ids: Vec<FillId>, image: Option<Uuid>) -> Self {
+        Self { layer_id, time, fill_ids, new_image: image, old: Vec::new() }
+    }
+
+    fn get_graph_mut<'a>(
+        document: &'a mut Document,
+        layer_id: &Uuid,
+        time: f64,
+    ) -> Result<&'a mut crate::vector_graph::VectorGraph, String> {
+        let layer = document
+            .get_layer_mut(layer_id)
+            .ok_or_else(|| format!("Layer {} not found", layer_id))?;
+        match layer {
+            AnyLayer::Vector(vl) => vl
+                .graph_at_time_mut(time)
+                .ok_or_else(|| format!("No keyframe at time {}", time)),
+            _ => Err("Not a vector layer".to_string()),
+        }
+    }
+}
+
+impl Action for SetImageFillAction {
+    fn execute(&mut self, document: &mut Document) -> Result<(), String> {
+        let graph = Self::get_graph_mut(document, &self.layer_id, self.time)?;
+        self.old.clear();
+        for &fid in &self.fill_ids {
+            self.old.push((fid, graph.fill(fid).image_fill));
+            graph.fill_mut(fid).image_fill = self.new_image;
+        }
+        Ok(())
+    }
+
+    fn rollback(&mut self, document: &mut Document) -> Result<(), String> {
+        let graph = Self::get_graph_mut(document, &self.layer_id, self.time)?;
+        for &(fid, old) in &self.old {
+            graph.fill_mut(fid).image_fill = old;
+        }
+        Ok(())
+    }
+
+    fn description(&self) -> String {
+        if self.new_image.is_some() { "Set image fill" } else { "Clear image fill" }.to_string()
+    }
+}

lightningbeam-ui/lightningbeam-editor/src/panes/infopanel.rs

@@ -12,7 +12,7 @@
 
 use eframe::egui::{self, DragValue, Ui};
 use lightningbeam_core::brush_settings::{bundled_brushes, BrushSettings};
-use lightningbeam_core::actions::{SetDocumentPropertiesAction, SetShapePropertiesAction, SetFillPaintAction};
+use lightningbeam_core::actions::{SetDocumentPropertiesAction, SetShapePropertiesAction, SetFillPaintAction, SetImageFillAction};
 use lightningbeam_core::gradient::ShapeGradient;
 use lightningbeam_core::layer::{AnyLayer, LayerTrait};
 use lightningbeam_core::selection::FocusSelection;
@@ -785,6 +785,26 @@ impl InfopanelPane {
         let edge_ids: Vec<lightningbeam_core::vector_graph::EdgeId> = shared.selection.selected_edges()
             .iter().map(|eid| lightningbeam_core::vector_graph::EdgeId(eid.0)).collect();
 
+        // Image-fill state for the selected fills + the document's image assets, for
+        // the picker below. Gathered now (immutable read) before `shared` is borrowed mut.
+        let image_assets: Vec<(Uuid, String)> = {
+            let doc = shared.action_executor.document();
+            let mut v: Vec<(Uuid, String)> = doc.image_assets.iter()
+                .map(|(id, a)| (*id, a.name.clone())).collect();
+            v.sort_by(|a, b| a.1.cmp(&b.1));
+            v
+        };
+        let current_image_fill: Option<Uuid> = {
+            let doc = shared.action_executor.document();
+            match doc.get_layer(&layer_id) {
+                Some(lightningbeam_core::layer::AnyLayer::Vector(vl)) => vl
+                    .graph_at_time(time)
+                    .and_then(|g| face_ids.first().map(|&fid| g.fill(fid).image_fill))
+                    .flatten(),
+                _ => None,
+            }
+        };
+
         egui::CollapsingHeader::new("Shape")
             .id_salt(("shape", path))
             .default_open(self.shape_section_open)
@@ -859,6 +879,33 @@ impl InfopanelPane {
                     }
                 }
 
+                // Image fill picker (assign/clear an imported image asset on the fill).
+                if !face_ids.is_empty() {
+                    ui.horizontal(|ui| {
+                        ui.label("Image:");
+                        let selected_text = current_image_fill
+                            .and_then(|id| image_assets.iter().find(|(aid, _)| *aid == id))
+                            .map(|(_, n)| n.clone())
+                            .unwrap_or_else(|| "None".to_string());
+                        egui::ComboBox::from_id_salt(("image_fill", path))
+                            .selected_text(selected_text)
+                            .show_ui(ui, |ui| {
+                                if ui.selectable_label(current_image_fill.is_none(), "None").clicked() {
+                                    shared.pending_actions.push(Box::new(
+                                        SetImageFillAction::new(layer_id, time, face_ids.clone(), None),
+                                    ));
+                                }
+                                for (aid, name) in &image_assets {
+                                    if ui.selectable_label(current_image_fill == Some(*aid), name).clicked() {
+                                        shared.pending_actions.push(Box::new(
+                                            SetImageFillAction::new(layer_id, time, face_ids.clone(), Some(*aid)),
+                                        ));
+                                    }
+                                }
+                            });
+                    });
+                }
+
                 // Stroke color
                 ui.horizontal(|ui| {
                     ui.label("Stroke:");