feat: upgrade prologue exploration presentation

docs/visual-asset-prologue-exploration-report.md

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+# Prologue exploration visual asset report
+
+Generated on 2026-07-26 with the built-in image generation workflow. These are
+original project assets; no commercial-game screenshot, logo, or third-party
+character artwork is included in the runtime files.
+
+## Runtime assets
+
+| Role | Project assets | Runtime format |
+| --- | --- | --- |
+| Zhuo village and militia camp | `src/assets/images/exploration/prologue-village.webp`, `prologue-militia-camp.webp` | 1920×1080 opaque WebP |
+| Exploration SD characters | `src/assets/images/exploration/characters/exploration-*.webp` | 3072×768 transparent WebP sprite sheets |
+| Prologue NPC dialogue portraits | `src/assets/images/portraits/zhuo-*-yellow-turban.webp`, `zou-jing-yellow-turban.webp` | 1254×1254 WebP |
+
+The two backgrounds reserve the exact top, right, and bottom HUD regions used
+by the 1920×1080 desktop layout. The playable portion was aligned to the
+existing collision and interaction coordinate system before export.
+
+Each exploration character sheet contains 192×192 frames: four direction rows
+(`south`, `east`, `north`, `west`) and sixteen columns per row (eight idle
+frames followed by eight walk frames). The SD characters are used only in
+exploration scenes; battle units retain their separate tactical sprites.
+
+## Final prompt set
+
+### Exploration backgrounds
+
+> Premium desktop historical-RPG exploration background, original
+> late-Eastern-Han settlement or militia camp, strict preservation of the
+> supplied road and landmark layout, elevated three-quarter orthographic
+> camera, rich painterly realistic materials, warm natural light, strong
+> small-character readability. No people, characters, text, UI, icons,
+> watermark, logo, modern objects, or copyrighted game screen.
+
+The village variant required the county office, tavern, recruiting hall,
+notice board, peach orchard, and north gate. The camp variant required the
+north gate, command tent, scout tent, sleeping tent, supply area, training
+area, and central fire.
+
+### Dialogue portraits
+
+> High-resolution realistic historical painting, late-Eastern-Han clothing,
+> warm dusty Yellow Turban-era palette, square face-and-shoulders composition
+> suitable for a dialogue window, natural skin and worn materials, original
+> identity distinct from the named heroes. No copied face, signature armor,
+> weapon, emblem, text, border, logo, watermark, or extra person.
+
+Role variants were a lean recruiting clerk, weathered middle-aged villager,
+practical quartermaster, disciplined local commander Zou Jing, and nervous
+young volunteer.
+
+### Exploration SD characters
+
+> Production game sprite turnaround for a desktop historical RPG. Create a
+> completely original 2.5-head-tall SD/chibi overworld character with a crisp
+> painterly cel-shaded silhouette. Exactly three equal vertical views:
+> front/south, right/east, back/north. Same identity, costume, scale, and
+> lighting in every view; full body and feet visible; neutral walking-ready
+> stance. Transparent or plain removable background. No floor, cast shadow,
+> scenery, grid, labels, text, logo, watermark, extra characters, duplicate
+> limbs, cropped body, or copyrighted game screen.
+
+The three hero turnarounds used this project's existing Yellow Turban-era
+portrait only as identity and palette reference. The recruiting clerk,
+villager, quartermaster, and Zou Jing then received dedicated turnarounds
+matched to their new dialogue portraits, so named characters no longer share
+one generic field sprite. The young volunteer uses the original militia
+infantry archetype. The west view is a mirrored side view, and restrained
+idle/walk motion frames were assembled from the turnarounds for consistent
+in-game scale.
+
+## Optimization and verification
+
+- Backgrounds are limited to 2 MiB each and 4 MiB combined.
+- SD sheets use transparent WebP and remain under 0.6 MiB each.
+- New NPC portraits were converted from generated PNG masters to high-quality
+  WebP, reducing the five-file total from about 11.6 MiB to about 1.3 MiB.
+- Static verifiers check background dimensions and opacity, sprite-sheet
+  dimensions and file coverage, and prologue speaker portrait coverage.