initial: Kotlin/Gradle skeleton for cloud-installer

Compiles to a 3.4 MB fat jar via shadow plugin.
Entrypoint with CLI dispatch (pull/push subcommands) + FlatLaf init.
Real sync logic stubbed; lands in subsequent commits per task plan.

Build via containerized gradle (8.10.2 + jdk21) to sidestep the
Kotlin 2.1 + JDK 26 compiler crash. Documented in README.

CI workflow tags-only release artifact upload prepared (needs
RELEASE_TOKEN secret in repo settings before first tag).

README.md

@@ -0,0 +1,81 @@
+# cloud-installer
+
+Single-jar Kotlin client for [`cloud-svc`](https://git.timemachine.center/Timemachine/cloud-svc). Drops into Prism / MMC / ATLauncher / frazclient pre-launch + post-exit hooks alongside [`packwiz-installer-bootstrap`](https://github.com/packwiz/packwiz-installer-bootstrap). One tool, all launchers, no Python dependency on the client side.
+
+## Status
+
+**Skeleton.** Build works, jar runs, CLI parses subcommands. Real sync logic + conflict UI land in subsequent commits. See [`DESIGN.md` in cloud-svc](https://git.timemachine.center/Timemachine/cloud-svc/src/branch/main/DESIGN.md) for the underlying contract this jar implements.
+
+## Usage (planned)
+
+In Prism's instance settings → Custom commands:
+
+```
+Pre-launch command:
+  "$INST_JAVA" -jar /path/to/cloud-installer.jar pull \
+      --url=https://cloud.timemachine.center \
+      --pack-folder=$INST_MC_DIR
+
+Post-exit command:
+  "$INST_JAVA" -jar /path/to/cloud-installer.jar push \
+      --url=https://cloud.timemachine.center \
+      --pack-folder=$INST_MC_DIR
+```
+
+Token comes from `$INST_MC_DIR/.cloud-token` (paste once from your Discord-bot DM), `--token <STR>`, or `CLOUD_TOKEN` env.
+
+## CLI
+
+```
+java -jar cloud-installer.jar <subcommand> [flags]
+
+Subcommands:
+  pull     Fetch user's cloud state, apply conflict resolution, write to instance.
+  push     Walk instance, build snapshot, upload changed files.
+
+Flags:
+  --url <URL>           cloud-svc base URL (required)
+  --pack-folder <DIR>   instance dir to sync into/from (default: ".")
+  --token <STR>         bearer token (or use --token-file)
+  --token-file <PATH>   read token from this file (default: <pack-folder>/.cloud-token)
+  -g, --no-gui          headless mode; conflicts auto-resolve to remote-wins
+  -V, --version         print version
+  -h, --help            print this help
+```
+
+## Build
+
+Requires JDK 17–21 (JDK 26 currently breaks Kotlin 2.1's compiler). Easiest: containerized via podman/docker.
+
+```bash
+podman run --rm -v "$PWD":/work:Z -w /work docker.io/gradle:8.10.2-jdk21 \
+    gradle --no-daemon shadowJar
+```
+
+Output: `build/libs/cloud-installer-<version>.jar`. Single fat jar; ship as-is.
+
+For local development with a matching JDK installed:
+
+```bash
+./gradlew shadowJar
+```
+
+## UI
+
+Swing + [FlatLaf](https://www.formdev.com/flatlaf/) (`FlatMacDarkLaf` theme). Closest visual match to Prism's Qt look in pure Java. Falls back to system look-and-feel if FlatLaf init fails (e.g., on bare-bones X servers).
+
+Conflict resolution dialog: per-file [keep local | use remote | skip] radio buttons + "use all local/remote" + Cancel/Continue. Headless mode (`-g`) defaults all conflicts to remote-wins (Steam's default).
+
+## Where this fits in the automc stack
+
+| Tool | What it owns |
+|---|---|
+| **packwiz-installer-bootstrap** | Mod sync — jars, configs shipped by the modpack, options.txt baseline |
+| **cloud-installer** (this) | Per-user sync — player-modified configs, JourneyMap waypoints, screenshots |
+| **frazclient** | Cracked-launcher orchestration — JDK, vanilla MC, Fabric, then invokes both jars |
+
+cloud-installer and packwiz-installer-bootstrap are deliberately **separate jars** so players can disable cloud sync without affecting modpack sync (or vice versa) by just commenting out the line in Prism's hook config.
+
+## License
+
+MIT.