tools: visual-review screenshot pipeline

- AGigLineShotActor (dev-only): walks a fixed camera list in -game mode,
  captures via FScreenshotRequest, quits. Test content only.
- ue_build_review_map.py builds /Game/Test/ReviewMap from current content
  (gray floor, key light, sky, MPFB character, 1 m scale cubes).
- render_screenshots.sh: build map -> run game -> collect PNGs into
  gitignored Screenshots/.
- Screenshots/README.md (committed) describes each capture with approval
  state; AGENTS.md gains the visual-review instructions.

Screenshots/README.md

@@ -0,0 +1,56 @@
+# Screenshots — visual review
+
+Rendered in-game captures of the current project content, generated by
+[`Tools/render_screenshots.sh`](../Tools/render_screenshots.sh). **The PNGs in
+this folder are never committed** (`.gitignore` excludes everything here
+except this README) — they exist on disk so a human can review the game's
+appearance after every change that could affect it.
+
+## How to regenerate
+
+```bash
+Tools/render_screenshots.sh
+```
+
+This rebuilds `Game/GigLine/Content/Test/ReviewMap.umap` from the current
+content (floor, key light, sky, MPFB character, the three 1 m scale cubes),
+runs the game on it in `-game` mode, lets `AGigLineShotActor` walk its fixed
+camera list and capture, and copies the PNGs here. Takes about a minute.
+
+Each screenshot is described below. After reviewing, mark the approval state
+in the table so agents know whether the look is accepted or needs work.
+
+## Current screenshots (generated 2026-11-07)
+
+| File | View | Shows | Approval |
+| --- | --- | --- | --- |
+| `review-00-overview.png` | Wide shot from the south-west, elevated | The review scene: character at origin, three 1 m calibration cubes in a row at 4 m north, gray floor, key light + sky | ☐ pending |
+| `review-01-character.png` | Medium shot, eye height, from the south | The MPFB-generated character with its baked skin material and A-pose bind | ☐ pending |
+| `review-02-scale-cubes.png` | Close three-quarter view of the cube row | The 1 m cubes for scale judgement against the character | ☐ pending |
+
+All captures are 2560×1440 PNG (the game window's size), unedited.
+
+## What to look for
+
+- **Character**: proportions, bind pose, skin material readability.
+- **Scale cubes**: each is exactly 1 m — use them to sanity-check anything
+  whose size looks off.
+- **Lighting**: one warm key light and fill sky; this is the temporary review
+  rig, not the `0.1.0` daytime look.
+
+## Known cosmetic issues in the review scene
+
+- The gray floor material renders with a speckled pattern instead of flat
+  gray — suspect the `Constant3Vector` wiring in `Tools/ue_build_review_map.py`.
+  Cosmetic only; the floor exists so shadows and scale read correctly.
+- The horizon shows a black band below the sky atmosphere (no distant ground
+  plane). Expected in the empty review scene.
+
+## Conventions
+
+- `review-NN-name.png` names are produced by `AGigLineShotActor`
+  (`Game/GigLine/Source/GigLine/GigLineShotActor.h`); the camera list lives in
+  `Tools/ue_build_review_map.py`.
+- Add or adjust shots there when new content needs review, then update this
+  README's table in the same change.
+- Agents: see the *Visual review* section in [`AGENTS.md`](../AGENTS.md).