Add fourth sequential asset expansion batch

docs/asset-backlog.md

@@ -6,9 +6,9 @@ generated, connected, validated, built, flow-tested, committed, and pushed.
 
 ## Current Baseline
 
-- Story images: 54 files after Batch 2.
-- Portraits: 26 files after Batch 2.
-- Unit sheets: 114 files, 57 complete base/action design pairs after Batch 3.
+- Story images: 64 files after Batch 4.
+- Portraits: 31 files after Batch 4.
+- Unit sheets: 122 files, 61 complete base/action design pairs after Batch 4.
 - Target direction:
   - Story: about 5 images per major campaign chapter across 65 campaign stages.
   - Portraits: one portrait for every important `scenario.ts` speaker.
@@ -113,4 +113,40 @@ Keep the existing texture keys so code paths and saved scenarios continue to wor
 
 ### Remaining Portraits
 
+- None. All currently mapped named speakers have portrait coverage after Batch 4.
+
+## Batch 4 Priority
+
+Status: complete. Image dimensions, unit base/action pairs, `pnpm build`, and `pnpm verify:flow` passed.
+
+This batch finishes the named-speaker portrait backlog, adds portrait variants that
+are actually selected in story scenes, and continues expanding high-repeat story
+backgrounds and class/faction unit variety.
+
+### Story
+
+- `55-yellow-pursuit-ambush.png`
+- `56-yellow-pursuit-village-relief.png`
+- `57-wolong-straw-boats.png`
+- `58-red-cliffs-wind-prayer.png`
+- `59-yiling-baidi-mountain-retreat.png`
+- `60-maicheng-isolation-snow-road.png`
+- `61-yiling-fire-attack-riverbank.png`
+- `62-hanzhong-rain-night-watch.png`
+- `63-weishui-northbank-cavalry-screen.png`
+- `64-nanzhong-forest-council.png`
+
+### Portraits
+
 - `ma-dai.png`
+- `liu-bei-campaign.png`
+- `guan-yu-campaign.png`
+- `zhang-fei-campaign.png`
+- `zhuge-liang-campaign.png`
+
+### Units
+
+- `unit-shu-spearman-veteran.png` + `unit-shu-spearman-veteran-actions.png`
+- `unit-wei-strategist-blue.png` + `unit-wei-strategist-blue-actions.png`
+- `unit-wu-officer-river.png` + `unit-wu-officer-river-actions.png`
+- `unit-nanman-officer-warlord.png` + `unit-nanman-officer-warlord-actions.png`