feat: add stature potions and tiny-player launchers

design/log.md

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+---
+type: Log
+title: Spigot Heights Design Log
+description: Chronological record of material decisions affecting Spigot Heights.
+---
+
+# Spigot Heights Design Log
+
+## 2026-09-04 — Initial design approved
+
+- Player scale defaults to a configurable range of `0.4` through `2.0`.
+- A moderate recipe creates a random stature potion; more expensive upgrades create targeted growth and diminution potions.
+- Random stature is selected uniformly in configurable `0.1` increments.
+- Players strictly below scale `0.5` can be launched through a dispenser fed by the hopper beneath them.
+- Launcher speed defaults to 1.5 blocks per tick with a 20-tick cooldown and safe-exit checks.
+- The project follows the neighboring Spigot Base Java 25, Purpur, Gradle, OKF, CI, and release conventions.
+
+## 2026-09-04 — Implementation started
+
+- Approved implementation began with user stories, tests, and the Gradle/Purpur foundation.