Document the experimental Ports install

The engine can now install native builds through Batocera's Ports system,
which is the other half of our catalog — cartridges are all this store
takes today. It stays off here: nobody has run one of these games on real
hardware yet, and each is a 30-100 MB download rather than a few kilobytes.

The README says how to switch it on per platform, which platforms have an
ARM build (so a Pi or a handheld skips the rest instead of installing
something that cannot start), and what the coverage measures at today.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -64,6 +64,55 @@ reach ROMs you put there yourself. To change any of it, edit
 `/userdata/system/batocera-store/ttg/config.json` on the box — the full key
 reference is in the engine's README.
 
+## Native games as Ports — experimental
+
+Cartridges are all this store installs by default, which is a little under half
+the catalog: the rest of our games are native builds, and an emulator cannot
+boot those. The engine can install them through Batocera's **Ports** system
+instead, but it is off here on purpose — **nobody has yet confirmed on real
+hardware that the games start**, and each one is a 30–100 MB download rather
+than a few kilobytes.
+
+To try it, add platform entries to
+`/userdata/system/batocera-store/ttg/config.json` on the box:
+
+```json
+"platforms": {
+  "ebitengine": {
+    "system": "ports",
+    "install": "port",
+    "kind": { "x86_64": "linux_x64", "aarch64": "linux_arm64" },
+    "ext": ".zip",
+    "enabled": true
+  },
+  "godot": { "system": "ports", "install": "port",
+             "kind": { "x86_64": "linux_x64" }, "ext": ".zip", "enabled": true },
+  "love":  { "system": "ports", "install": "port",
+             "kind": { "x86_64": "linux_x64" }, "ext": ".zip", "enabled": true },
+  "bevy":  { "system": "ports", "install": "port",
+             "kind": { "x86_64": "linux_x64", "aarch64": "linux_arm64" },
+             "ext": ".zip", "enabled": true }
+}
+```
+
+Then `/userdata/system/batocera-store/ttg-store sync`. The games appear under
+*Ports ▸ Teletype Games*; `remove` takes the unpacked program with it.
+
+**Mind the architecture.** Only the platforms listed with an `aarch64` entry
+above have ARM builds today — on a Raspberry Pi or a handheld the others are
+skipped with a message naming the architecture, rather than installing something
+that cannot start. `godot`, `love` and `tic80` have no ARM build at all yet: a
+Godot ARM export needs a preset in the game repo, LÖVE has no upstream ARM
+runtime, and TIC-80's exporter has no ARM target.
+
+With everything that can be enabled turned on, the coverage measured on
+2026-08-17 was **13 of 15** titles on x86_64 and **9 of 15** on ARM. The two that
+stay out either way are `phaserdemo` and `trickster-tiles`: they ship only a web
+build.
+
+Report back what happens on a real box — that is the missing piece before this
+becomes the default.
+
 ## Where things land
 
 ```