Add purge and an uninstaller, and move to the stores org

`purge` is what `remove` does for one game, for all of them at once, plus the
directories the store made: the shell script that wraps it has no way of knowing
which ROMs, box art, Ports payloads and gamelist entries were ours, and
state.json does. uninstall.sh runs it first and only then removes the Ports
entry, the launcher and the store home; if the engine cannot finish, nothing
else is touched.

The gamelists are merged rather than deleted — they belong to the box, and the
user's own games, play counts and favourites stay in them. Two things the tests
caught:

- The backup was being made on the *uninstall's* first touch of a gamelist we
  had created ourselves, so a purge produced a backup of our own file. It is now
  skipped when purging: by then any copy worth having was made on the first sync.
- With that fixed, "no backup next to it" means we created the file, so a
  gamelist that is left empty is deleted too. The box ends up as it was.
- The Ports entry cannot be derived from the config: a store repository sets
  BATOCERA_PORT_NAME to whatever it likes (ours is "Teletype Games Store" while
  store.name is "Teletype Games"), so the uninstaller looked for a file that was
  never there. It now finds the entry by looking inside the Ports scripts for
  this store's home — which also works for boxes installed before this existed,
  and picks up entries left over from an earlier name.

install.sh and uninstall.sh are POSIX sh now, checked with dash, so `curl … | sh`
works where /bin/sh is not bash. The repository moved from the tools org to
stores; the old raw URLs still redirect, but every reference is updated.

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

README.md

@@ -10,7 +10,7 @@ about any particular site: the host, the store's name and where its games land
 all come from a `config.json` that lives in a separate **store repository**.
 The part that is not about Batocera — catalog, releases, host matching, state,
 HTTP — is [`warpstore`](https://git.teletypegames.org/engines/warpstore), shared
-with the [RetroArch engine](https://git.teletypegames.org/tools/warp-engine-retroarch-store).
+with the [RetroArch engine](https://git.teletypegames.org/stores/warp-engine-retroarch-store).
 
 ```
 warpstore                           the shared core — warpstore.py
@@ -28,7 +28,7 @@ teletypegames.org   my.example   other.example
 ```
 
 The reference store is
-[`ttg-batocera-store`](https://git.teletypegames.org/tools/ttg-batocera-store).
+[`ttg-batocera-store`](https://git.teletypegames.org/stores/ttg-batocera-store).
 
 ```
 Ports ▸ "<store name>"
@@ -48,8 +48,8 @@ Python 3 standard library only — Batocera ships python3 and no pip.
 The installer takes the store as a parameter, so it works with any config:
 
 ```sh
-STORE_CONFIG=https://git.example.org/tools/my-store/raw/branch/master/config.json \
-  bash <(curl -fsSL https://git.teletypegames.org/tools/warp-engine-batocera-store/raw/branch/master/install.sh)
+curl -fsSL https://git.teletypegames.org/stores/warp-engine-batocera-store/raw/branch/master/install.sh |
+  STORE_CONFIG=https://git.example.org/tools/my-store/raw/branch/master/config.json sh
 ```
 
 From a checkout, with a local config:
@@ -75,12 +75,13 @@ Installer knobs, all environment variables: `STORE_CONFIG` (required),
 
 ## Writing a store repository
 
-Three files:
+Four small files:
 
 ```
 my-batocera-store/
 ├── config.json     the store: URL, name, subfolder, platform mapping
 ├── install.sh      a wrapper that hands that config to the engine installer
+├── uninstall.sh    the same for the engine's uninstaller
 └── README.md
 ```
 
@@ -89,10 +90,18 @@ my-batocera-store/
 ```sh
 #!/bin/bash
 set -euo pipefail
-ENGINE_RAW_BASE="${ENGINE_RAW_BASE:-https://git.teletypegames.org/tools/warp-engine-batocera-store/raw/branch/master}"
+ENGINE_RAW_BASE="${ENGINE_RAW_BASE:-https://git.teletypegames.org/stores/warp-engine-batocera-store/raw/branch/master}"
 export STORE_CONFIG="${STORE_CONFIG:-https://git.example.org/tools/my-batocera-store/raw/branch/master/config.json}"
 export BATOCERA_PORT_NAME="My Store"
-curl -fsSL "$ENGINE_RAW_BASE/install.sh" | bash
+curl -fsSL "$ENGINE_RAW_BASE/install.sh" | sh
+```
+
+`uninstall.sh` is the same shape, except that it passes `STORE_ID` — no config
+fetch is needed to take a store away, and the id is what names its home:
+
+```sh
+export STORE_ID="${STORE_ID:-example}"
+curl -fsSL "$ENGINE_RAW_BASE/uninstall.sh" | sh
 ```
 
 Pick a `store.id` and a `paths.subfolder` nobody else uses — they are what keeps
@@ -114,11 +123,51 @@ $S sync                 # download everything new, refresh gamelists
 $S sync blessingofra    # just one title (never prunes)
 $S -n sync              # dry run
 $S remove c64:demo      # uninstall (bare name works too)
+$S purge                # uninstall everything this store installed
 $S config               # effective configuration
 ```
 
 Global flags go **before** the subcommand: `$S --roms-root /tmp/roms sync`.
 
+## Uninstalling
+
+```sh
+ssh root@batocera 'curl -fsSL https://git.teletypegames.org/stores/warp-engine-batocera-store/raw/branch/master/uninstall.sh | sh'
+```
+
+or `./uninstall.sh` from a checkout on the box. It removes the games first,
+through the engine — `purge` — and only then the Ports entry, the launcher and the
+store home: the shell script has no way of knowing which ROMs, box art, Ports
+payloads and gamelist entries were the store's, and the engine's `state.json`
+does. If the engine cannot finish — an unmounted ROMs root, say — nothing else is
+touched, so you are never left with the files but not the engine that knows about
+them.
+
+| Environment variable | Meaning |
+|---|---|
+| `STORE_ID` | which store to remove; needed only when several are installed |
+| `STORE_CONFIG` | alternative to `STORE_ID` — the id is read out of the config |
+| `DRY_RUN` | `1` to print what would go and remove nothing |
+| `KEEP_HOME` | `1` to keep the store home (state, catalog cache, log) for a reinstall |
+| `BATOCERA_STORE_ROOT`, `BATOCERA_PORTS_DIR`, `BATOCERA_PORT_NAME` | as for the installer |
+
+What it deliberately leaves behind:
+
+- **ROMs you put in the store's subfolder yourself.** Directories are removed only when empty, so one stray file keeps its directory. `ports/.data` itself also stays: another store may still keep a payload there.
+- **your gamelists.** They belong to the box: our `<game>` and `<folder>` nodes go, the rest — your own games, their play counts and favourites — is written back untouched. A gamelist we *created* and that is left empty is deleted, since it was never yours.
+- **`gamelist.xml.<store id>-backup`**, listed at the end of the run: your gamelists as we first found them. Deleting them is your call.
+
+A dry run cannot predict which directories will end up empty, so it lists the
+files but not the directory removals.
+
+To take **every** store off a machine — both engines, the shared core, the
+launchers — there is one script for that in
+[`warpstore`](https://git.teletypegames.org/engines/warpstore):
+
+```sh
+curl -fsSL https://git.teletypegames.org/engines/warpstore/raw/branch/master/uninstall.sh | sh
+```
+
 ## Where things land
 
 ```