Bundles carry pre-baked backgrounds (paintings survive filesystem-less boots)

RoomDoc gains baked_visual (quantized indices, exporter-written, skipped when empty); bake() falls back to it when pics/ can't load; --export-bundle folds every room's painting in via World::bake_backgrounds_for_bundle. A six-painting game bundles to 1.5MB. Tests green; alley renders from bundle alone with no pics/ on disk.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

mrpci-core/src/bin/mrpci-headless/main.rs

@@ -76,7 +76,11 @@ fn main() {
     let mut gs = GameState::new(world);
 
     if let Some(path) = get("--export-bundle") {
-        let bundle = gs.world.to_bundle();
+        let mut bundle = gs.world.to_bundle();
+        // Paintings ride inside the bundle as pre-quantized indices, so the
+        // wasm build (no filesystem) keeps its backgrounds.
+        gs.world.bake_backgrounds_for_bundle(&mut bundle.rooms);
+        let bundle = bundle;
         // Through Value first, so the output is byte-stable.
         //
         // A bundle is full of HashMaps — rooms, scripts, sprites, every

mrpci-core/src/room.rs

@@ -154,6 +154,12 @@ pub struct RoomDoc {
     /// `<name>-ctl.png` companions). Applied before `ops`.
     #[serde(default)]
     pub background: String,
+    /// The background pre-quantized to visual indices (PIC_W*PIC_H), written
+    /// by the bundle exporter so filesystem-less builds (wasm) keep their
+    /// paintings. Only consulted when the `pics/` file can't be loaded;
+    /// travels with `palette`, which the exporter sets to the quantized one.
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub baked_visual: Vec<u8>,
     /// Procedural paint ops (replayed after the background, if any).
     #[serde(default)]
     pub ops: Vec<PicOp>,
@@ -207,6 +213,7 @@ impl Default for RoomDoc {
             name: String::new(),
             enter_text: String::new(),
             background: String::new(),
+            baked_visual: Vec::new(),
             ops: Vec::new(),
             palette: None,
             cycles: Vec::new(),
@@ -395,6 +402,10 @@ impl World {
             let dir = self.base.join("pics");
             if let Some(rgba) = assets::load_rgba_scaled(&dir.join(format!("{}.png", self.doc.background)), PIC_W, PIC_H) {
                 assets::bake_background(&rgba, &mut self.palette, &mut self.screens);
+            } else if self.doc.baked_visual.len() == PIC_W * PIC_H {
+                // No filesystem (or the art moved): the exporter pre-baked
+                // the painting into the doc. Palette came from doc.palette.
+                self.screens.visual.copy_from_slice(&self.doc.baked_visual);
             }
             if let Some(rgba) = assets::load_rgba_scaled(&dir.join(format!("{}-pri.png", self.doc.background)), PIC_W, PIC_H) {
                 assets::bake_pri_mask(&rgba, &mut self.screens);
@@ -518,6 +529,25 @@ impl World {
         WorldBundle { manifest: self.manifest.clone(), rooms, scripts, sprites }
     }
 
+    /// Fold each room's background painting into its doc (quantized indices
+    /// + palette), so the bundle plays where there is no filesystem. The
+    /// exporter calls this; docs already carrying a bake are left alone.
+    pub fn bake_backgrounds_for_bundle(&self, rooms: &mut BTreeMap<u32, RoomDoc>) {
+        for doc in rooms.values_mut() {
+            if doc.background.is_empty() || doc.baked_visual.len() == PIC_W * PIC_H {
+                continue;
+            }
+            let dir = self.base.join("pics");
+            if let Some(rgba) = assets::load_rgba_scaled(&dir.join(format!("{}.png", doc.background)), PIC_W, PIC_H) {
+                let mut pal = doc.palette.clone().unwrap_or_else(Palette::base);
+                let mut probe = Screens::new();
+                assets::bake_background(&rgba, &mut pal, &mut probe);
+                doc.palette = Some(pal);
+                doc.baked_visual = probe.visual;
+            }
+        }
+    }
+
     /// Replace the loaded world with a bundle. A bundle that carries
     /// sprites replaces the art wholesale (the wasm/bootstrap path); one
     /// that doesn't keeps whatever this World already loaded.