refactor: rename coordinates — parent + zstd-java library

- root aggregator artifactId: zstd-java -> parent
- library module: core/ -> zstd/, artifactId zstd-java-core -> zstd-java
  (the official coordinate: io.github.dfa1:zstd-java)
- native/bom artifacts keep the zstd-java-* prefix
- relocate the vendored submodule zstd/ -> third_party/zstd to free the zstd/
  dir for the module; update .gitmodules and build-zstd.sh accordingly
- refresh README/CLAUDE paths

40 tests green, checkstyle clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dfa1

.gitmodules

@@ -1,3 +1,3 @@
 [submodule "zstd"]
-	path = zstd
+	path = third_party/zstd
 	url = https://github.com/facebook/zstd.git

CLAUDE.md

@@ -11,14 +11,14 @@ already off-heap (e.g. an mmap slice in, an arena buffer out).
 
 Multi-module Maven build (`io.github.dfa1:zstd-java`):
 
-- `core/` — pure-Java FFM bindings (package `io.github.dfa1.zstdffm`). The only
-  module with Java sources.
+- `zstd/` — the library module, artifactId `zstd-java`, pure-Java FFM bindings
+  (package `io.github.dfa1.zstdffm`). The only module with Java sources.
 - `native/<classifier>/` — one module per platform; each packages a
-  `libzstd.{dylib,so,dll}` built from the `zstd/` submodule. No Java.
+  `libzstd.{dylib,so,dll}` built from the `third_party/zstd` submodule. No Java.
   Classifiers: `osx-aarch64`, `osx-x86_64`, `linux-x86_64`, `linux-aarch64`,
   `windows-x86_64`, `windows-aarch64`.
 - `bom/` — dependency BOM.
-- `zstd/` — vendored `facebook/zstd` git submodule (the C source of truth).
+- `third_party/zstd/` — vendored `facebook/zstd` git submodule (the C source of truth).
 
 ## Native build
 
@@ -81,4 +81,4 @@ Built `.dylib/.so/.dll` are git-ignored; they are regenerated from the submodule
   `<strong>`,`<pre>`,`<table>`, …). Use blank `///` for paragraphs, `- ` lists, ` ```java ``` `,
   `**bold**`. Cross-refs `[ClassName#method(ParamType)]` — verify the target exists (wrong refs are
   **errors**).
-- Check: `./mvnw javadoc:javadoc -pl core` must produce zero output.
+- Check: `./mvnw javadoc:javadoc -pl zstd` must produce zero output.

README.md

@@ -22,7 +22,8 @@ libc for every target, enabling hermetic cross-compilation without a sysroot.
 
 ## Supported platforms
 
-The library ships as pure-Java `core` plus one native artifact per platform:
+The library — `io.github.dfa1:zstd-java` — ships as a pure-Java module plus one
+native artifact per platform:
 
 | OS      | aarch64 | x86_64 |
 |---------|:-------:|:------:|
@@ -118,7 +119,7 @@ mvn test
 ```
 
 The `mvn` build invokes `scripts/build-zstd.sh`, which compiles
-`libzstd.{dylib,so,dll}` from the `zstd/` submodule with `zig cc`. The script
+`libzstd.{dylib,so,dll}` from the `third_party/zstd` submodule with `zig cc`. The script
 cross-compiles any of the six targets from any host:
 
 ```bash

bom/pom.xml

@@ -4,7 +4,7 @@
 
 	<parent>
 		<groupId>io.github.dfa1</groupId>
-		<artifactId>zstd-java</artifactId>
+		<artifactId>parent</artifactId>
 		<version>0.1-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
@@ -17,7 +17,7 @@
 		<dependencies>
 			<dependency>
 				<groupId>io.github.dfa1</groupId>
-				<artifactId>zstd-java-core</artifactId>
+				<artifactId>zstd-java</artifactId>
 				<version>${project.version}</version>
 			</dependency>
 			<dependency>

native/linux-aarch64/pom.xml

@@ -4,7 +4,7 @@
 
 	<parent>
 		<groupId>io.github.dfa1</groupId>
-		<artifactId>zstd-java</artifactId>
+		<artifactId>parent</artifactId>
 		<version>0.1-SNAPSHOT</version>
 		<relativePath>../../pom.xml</relativePath>
 	</parent>

native/linux-x86_64/pom.xml

@@ -4,7 +4,7 @@
 
 	<parent>
 		<groupId>io.github.dfa1</groupId>
-		<artifactId>zstd-java</artifactId>
+		<artifactId>parent</artifactId>
 		<version>0.1-SNAPSHOT</version>
 		<relativePath>../../pom.xml</relativePath>
 	</parent>

native/osx-aarch64/pom.xml

@@ -4,7 +4,7 @@
 
 	<parent>
 		<groupId>io.github.dfa1</groupId>
-		<artifactId>zstd-java</artifactId>
+		<artifactId>parent</artifactId>
 		<version>0.1-SNAPSHOT</version>
 		<relativePath>../../pom.xml</relativePath>
 	</parent>

native/osx-x86_64/pom.xml

@@ -4,7 +4,7 @@
 
 	<parent>
 		<groupId>io.github.dfa1</groupId>
-		<artifactId>zstd-java</artifactId>
+		<artifactId>parent</artifactId>
 		<version>0.1-SNAPSHOT</version>
 		<relativePath>../../pom.xml</relativePath>
 	</parent>

native/windows-aarch64/pom.xml

@@ -4,7 +4,7 @@
 
 	<parent>
 		<groupId>io.github.dfa1</groupId>
-		<artifactId>zstd-java</artifactId>
+		<artifactId>parent</artifactId>
 		<version>0.1-SNAPSHOT</version>
 		<relativePath>../../pom.xml</relativePath>
 	</parent>

native/windows-x86_64/pom.xml

@@ -4,7 +4,7 @@
 
 	<parent>
 		<groupId>io.github.dfa1</groupId>
-		<artifactId>zstd-java</artifactId>
+		<artifactId>parent</artifactId>
 		<version>0.1-SNAPSHOT</version>
 		<relativePath>../../pom.xml</relativePath>
 	</parent>