docs: add latent cache guidance

Author: ReverseZoom2151

README.md

@@ -44,6 +44,7 @@ See [human-evaluation guidance](docs/HUMAN_EVALUATION.md) before running a
 blinded participant study.
 See the [security policy](docs/SECURITY.md) for CI gates and responsible
 disclosure guidance.
+See [latent-cache guidance](docs/LATENT_CACHE.md) before precomputing VAE data.
 
 ## Commands
 

docs/LATENT_CACHE.md

@@ -0,0 +1,15 @@
+# Latent cache
+
+Use `gamengen-cache-latents` only on validated NPZ recording shards. The command
+loads the revision pinned in the selected configuration and stores one latent per
+source frame, along with the original transition arrays and source-shard SHA-256.
+
+```bash
+gamengen-cache-latents --config configs/tier2_doom_lite.yaml \
+  --shard data/recordings/shard_000000.npz \
+  --output data/latents/shard_000000.npz
+```
+
+A cache is invalid when its source-shard checksum differs. Regenerate it after
+changing recordings, preprocessing, model revision, or VAE encoding behavior.
+The cache format is safe NPZ only; it never loads pickle artifacts.