feat(init): 支持补齐内置模板空目录

新增 init 子命令，根据项目中的 world_*_packs.json 解析实际包目录并创建标准空目录。

改用 .empty-dirs 维护内置模板空目录清单，删除会污染用户项目和网易 Bedrock 加载流程的 .gitkeep 占位文件。

build.rs

@@ -1,8 +1,11 @@
 use std::{
+    collections::BTreeMap,
     env, fs, io,
     path::{Path, PathBuf},
 };
 
+const EMPTY_DIRS_FILE: &str = ".empty-dirs";
+
 fn main() {
     println!("cargo:rerun-if-changed=examples");
 
@@ -12,25 +15,37 @@ fn main() {
 
     let mut dirs = Vec::new();
     let mut files = Vec::new();
+    let mut empty_dirs_by_example = BTreeMap::new();
 
     if examples_root.is_dir() {
-        collect_examples(&examples_root, &examples_root, &mut dirs, &mut files)
-            .expect("failed to collect example templates");
+        collect_examples(
+            &examples_root,
+            &examples_root,
+            &mut dirs,
+            &mut files,
+            &mut empty_dirs_by_example,
+        )
+        .expect("failed to collect example templates");
     }
 
     dirs.sort();
+    dirs.dedup();
     files.sort_by(|a, b| a.0.cmp(&b.0));
+    for empty_dirs in empty_dirs_by_example.values_mut() {
+        empty_dirs.sort();
+        empty_dirs.dedup();
+    }
 
     let mut generated = String::new();
     generated.push_str(
-        "struct EmbeddedFile {\n    path: &'static str,\n    contents: &'static [u8],\n}\n\n",
+        "#[allow(dead_code)]\nstruct EmbeddedFile {\n    path: &'static str,\n    contents: &'static [u8],\n}\n\n",
     );
-    generated.push_str("static EMBEDDED_EXAMPLE_DIRS: &[&str] = &[\n");
+    generated.push_str("#[allow(dead_code)]\nstatic EMBEDDED_EXAMPLE_DIRS: &[&str] = &[\n");
     for dir in &dirs {
         generated.push_str(&format!("    {:?},\n", dir));
     }
     generated.push_str("];\n\n");
-    generated.push_str("static EMBEDDED_EXAMPLE_FILES: &[EmbeddedFile] = &[\n");
+    generated.push_str("#[allow(dead_code)]\nstatic EMBEDDED_EXAMPLE_FILES: &[EmbeddedFile] = &[\n");
     for (relative_path, absolute_path) in &files {
         generated.push_str(&format!(
             "    EmbeddedFile {{ path: {:?}, contents: include_bytes!(r#\"{}\"#) }},\n",
@@ -38,6 +53,23 @@ fn main() {
             absolute_path.display()
         ));
     }
+    generated.push_str("];\n\n");
+    generated.push_str(
+        "#[allow(dead_code)]\nstruct EmbeddedExampleEmptyDirs {\n    example: &'static str,\n    dirs: &'static [&'static str],\n}\n\n",
+    );
+    generated.push_str(
+        "#[allow(dead_code)]\nstatic EMBEDDED_EXAMPLE_EMPTY_DIRS: &[EmbeddedExampleEmptyDirs] = &[\n",
+    );
+    for (example, empty_dirs) in &empty_dirs_by_example {
+        generated.push_str(&format!(
+            "    EmbeddedExampleEmptyDirs {{ example: {:?}, dirs: &[\n",
+            example
+        ));
+        for dir in empty_dirs {
+            generated.push_str(&format!("        {:?},\n", dir));
+        }
+        generated.push_str("    ] },\n");
+    }
     generated.push_str("];\n");
 
     fs::write(out_file, generated).expect("failed to write embedded example list");
@@ -48,6 +80,7 @@ fn collect_examples(
     dir: &Path,
     dirs: &mut Vec<String>,
     files: &mut Vec<(String, PathBuf)>,
+    empty_dirs_by_example: &mut BTreeMap<String, Vec<String>>,
 ) -> io::Result<()> {
     for entry in fs::read_dir(dir)? {
         let entry = entry?;
@@ -60,11 +93,50 @@ fn collect_examples(
 
         if path.is_dir() {
             dirs.push(relative_path);
-            collect_examples(root, &path, dirs, files)?;
+            collect_examples(root, &path, dirs, files, empty_dirs_by_example)?;
         } else if path.is_file() {
-            files.push((relative_path, path.canonicalize()?));
+            if path.file_name().and_then(|name| name.to_str()) == Some(EMPTY_DIRS_FILE) {
+                collect_empty_dirs(&relative_path, &path, dirs, empty_dirs_by_example)?;
+            } else {
+                files.push((relative_path, path.canonicalize()?));
+            }
         }
     }
 
     Ok(())
 }
+
+fn collect_empty_dirs(
+    relative_path: &str,
+    path: &Path,
+    dirs: &mut Vec<String>,
+    empty_dirs_by_example: &mut BTreeMap<String, Vec<String>>,
+) -> io::Result<()> {
+    let (example, file_name) = relative_path.split_once('/').ok_or_else(|| {
+        io::Error::new(
+            io::ErrorKind::InvalidData,
+            format!("{} must be inside an example directory", EMPTY_DIRS_FILE),
+        )
+    })?;
+    if file_name != EMPTY_DIRS_FILE {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidData,
+            format!("unexpected {} path: {}", EMPTY_DIRS_FILE, relative_path),
+        ));
+    }
+
+    let contents = fs::read_to_string(path)?;
+    let empty_dirs = empty_dirs_by_example
+        .entry(example.to_string())
+        .or_insert_with(Vec::new);
+    for line in contents.lines() {
+        let dir = line.trim();
+        if dir.is_empty() || dir.starts_with('#') {
+            continue;
+        }
+        dirs.push(format!("{}/{}", example, dir));
+        empty_dirs.push(dir.to_string());
+    }
+
+    Ok(())
+}