Document placement plan printer

README.md

@@ -50,6 +50,11 @@ positions and sizes, wander radius, calibration readouts. Marker print size stay
   exact same `anchorWorldMatrix` the AR pipeline uses, each with a white orientation arrow;
   compass rose on the grid (N = +Z = back of table). Top-view button, property panel,
   save/reset-to-seed.
+- **Placement plan printer** (`/admin/plan.html`): to-scale top-down plan of the whole
+  layout — at 1:1 the actual crest patterns print true-size in position, so you can tape
+  the sheets to the table and the markers are already placed. Tiles across A4/A3 with
+  10 mm overlap, crop marks, join labels (A1/B2…), overview page with tile map, per-layer
+  toggles, grid ruler and compass. 1:2 / 1:5 / fit scales for checking proportions.
 - **Playlist manager** (`/admin/playlist.html`), **crest print sheet** (`/admin/print.html`,
   true-to-size), **calibration** (`/admin/calibrate.html`: live distance/angle/jitter +
   fused pose), **client error log** (`/admin/errors.html`).