feat: FileReadTool image support + FileEditTool unified diff output

- FileReadTool: detect image files (png/jpg/gif/webp/svg/bmp/ico),
  read as Base64 with MIME type, 20MB size limit
- FileEditTool: generate unified diff after edits with 3-line context,
  showing removed (-) and added (+) lines in standard diff format

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/java/com/claudecode/tool/impl/FileEditTool.java

@@ -15,6 +15,7 @@ import java.util.Map;
  * 文件编辑工具 —— 对应 claude-code/src/tools/edit/EditFileTool.ts。
  * <p>
  * 通过精确匹配 old_string 并替换为 new_string 来编辑文件。
+ * 编辑后返回 unified diff 格式的变更摘要。
  */
 public class FileEditTool implements Tool {
 
@@ -91,17 +92,88 @@ public class FileEditTool implements Tool {
             String newContent = content.substring(0, firstIdx) + newString + content.substring(firstIdx + oldString.length());
             Files.writeString(path, newContent, StandardCharsets.UTF_8);
 
-            // 计算变更范围
+            // 生成 unified diff 摘要
+            String diff = generateUnifiedDiff(path.toString(), content, newContent);
+
+            // 计算变更统计
             long oldLines = oldString.lines().count();
             long newLines = newString.lines().count();
 
-            return "✅ Edited " + path + " (replaced " + oldLines + " lines with " + newLines + " lines)";
+            StringBuilder result = new StringBuilder();
+            result.append("✅ Edited ").append(path)
+                    .append(" (replaced ").append(oldLines)
+                    .append(" lines with ").append(newLines).append(" lines)\n\n");
+            result.append(diff);
+
+            return result.toString().stripTrailing();
 
         } catch (IOException e) {
             return "Error editing file: " + e.getMessage();
         }
     }
 
+    /**
+     * 生成 unified diff 格式输出。
+     * 类似 TS 版本的 getPatchForEdit()，但使用纯 Java 实现。
+     */
+    private String generateUnifiedDiff(String filePath, String original, String modified) {
+        List<String> oldLines = original.lines().collect(java.util.stream.Collectors.toList());
+        List<String> newLines = modified.lines().collect(java.util.stream.Collectors.toList());
+
+        // 找出变更区域
+        int contextLines = 3;
+
+        // 找到第一个不同的行
+        int firstDiff = 0;
+        int minLen = Math.min(oldLines.size(), newLines.size());
+        while (firstDiff < minLen && oldLines.get(firstDiff).equals(newLines.get(firstDiff))) {
+            firstDiff++;
+        }
+
+        // 找到最后一个不同的行（从末尾向前扫描）
+        int oldEnd = oldLines.size();
+        int newEnd = newLines.size();
+        while (oldEnd > firstDiff && newEnd > firstDiff
+                && oldLines.get(oldEnd - 1).equals(newLines.get(newEnd - 1))) {
+            oldEnd--;
+            newEnd--;
+        }
+
+        // 计算包含上下文的范围
+        int ctxStart = Math.max(0, firstDiff - contextLines);
+        int oldCtxEnd = Math.min(oldLines.size(), oldEnd + contextLines);
+        int newCtxEnd = Math.min(newLines.size(), newEnd + contextLines);
+
+        StringBuilder sb = new StringBuilder();
+        sb.append("--- a/").append(filePath).append('\n');
+        sb.append("+++ b/").append(filePath).append('\n');
+
+        // Hunk header: @@ -oldStart,oldCount +newStart,newCount @@
+        int oldHunkSize = oldCtxEnd - ctxStart;
+        int newHunkSize = newCtxEnd - ctxStart - (oldEnd - firstDiff) + (newEnd - firstDiff);
+        sb.append(String.format("@@ -%d,%d +%d,%d @@%n",
+                ctxStart + 1, oldHunkSize, ctxStart + 1, newHunkSize));
+
+        // Context before
+        for (int i = ctxStart; i < firstDiff; i++) {
+            sb.append(' ').append(oldLines.get(i)).append('\n');
+        }
+        // Removed lines
+        for (int i = firstDiff; i < oldEnd; i++) {
+            sb.append('-').append(oldLines.get(i)).append('\n');
+        }
+        // Added lines
+        for (int i = firstDiff; i < newEnd; i++) {
+            sb.append('+').append(newLines.get(i)).append('\n');
+        }
+        // Context after
+        for (int i = oldEnd; i < oldCtxEnd; i++) {
+            sb.append(' ').append(oldLines.get(i)).append('\n');
+        }
+
+        return sb.toString();
+    }
+
     @Override
     public String activityDescription(Map<String, Object> input) {
         return "✏️ Editing " + input.getOrDefault("file_path", "file");

src/main/java/com/claudecode/tool/impl/FileReadTool.java

@@ -7,19 +7,28 @@ import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.Base64;
 import java.util.Map;
-import java.util.stream.Collectors;
+import java.util.Set;
 
 /**
  * 文件读取工具 —— 对应 claude-code/src/tools/read/ReadFileTool.ts。
  * <p>
- * 读取文件内容，支持行号范围过滤。
+ * 读取文件内容，支持行号范围过滤和图片读取（Base64编码）。
  */
 public class FileReadTool implements Tool {
 
     /** 单次读取最大行数 */
     private static final int MAX_LINES = 2000;
 
+    /** 图片最大文件大小 (20MB) */
+    private static final long MAX_IMAGE_SIZE = 20 * 1024 * 1024;
+
+    /** 支持的图片扩展名 */
+    private static final Set<String> IMAGE_EXTENSIONS = Set.of(
+            "png", "jpg", "jpeg", "gif", "webp", "svg", "bmp", "ico"
+    );
+
     @Override
     public String name() {
         return "Read";
@@ -28,8 +37,10 @@ public class FileReadTool implements Tool {
     @Override
     public String description() {
         return """
-            Read the contents of a file. Use line_start and line_end to read specific line ranges. \
+            Read the contents of a file. Supports text files with optional line ranges, \
-            For large files, read in chunks. Supports text files only.""";
+            and image files (png, jpg, jpeg, gif, webp, svg, bmp, ico) which are returned \
+            as Base64-encoded data with MIME type. For large text files, read in chunks \
+            using line_start and line_end.""";
     }
 
     @Override
@@ -44,11 +55,11 @@ public class FileReadTool implements Tool {
                 },
                 "line_start": {
                   "type": "integer",
-                  "description": "Starting line number (1-based, inclusive)"
+                  "description": "Starting line number (1-based, inclusive). Only for text files."
                 },
                 "line_end": {
                   "type": "integer",
-                  "description": "Ending line number (1-based, inclusive)"
+                  "description": "Ending line number (1-based, inclusive). Only for text files."
                 }
               },
               "required": ["file_path"]
@@ -72,6 +83,47 @@ public class FileReadTool implements Tool {
             return "Error: Not a regular file: " + path;
         }
 
+        // Check if it's an image file
+        String ext = getExtension(path.getFileName().toString());
+        if (IMAGE_EXTENSIONS.contains(ext)) {
+            return readImage(path, ext);
+        }
+
+        // Text file reading
+        return readText(path, input);
+    }
+
+    /**
+     * 读取图片文件，返回 Base64 编码数据和 MIME 类型信息。
+     */
+    private String readImage(Path path, String ext) {
+        try {
+            long size = Files.size(path);
+            if (size > MAX_IMAGE_SIZE) {
+                return "Error: Image too large (" + formatSize(size) + "). Max: " + formatSize(MAX_IMAGE_SIZE);
+            }
+            if (size == 0) {
+                return "Error: Image file is empty: " + path;
+            }
+
+            byte[] bytes = Files.readAllBytes(path);
+            String base64 = Base64.getEncoder().encodeToString(bytes);
+            String mimeType = getMimeType(ext);
+
+            return String.format("""
+                {"type": "image", "file_path": "%s", "mime_type": "%s", \
+                "size": %d, "base64_length": %d, "base64": "%s"}""",
+                    escapeJson(path.toString()), mimeType, size, base64.length(), base64);
+
+        } catch (IOException e) {
+            return "Error reading image: " + e.getMessage();
+        }
+    }
+
+    /**
+     * 读取文本文件，支持行范围过滤。
+     */
+    private String readText(Path path, Map<String, Object> input) {
         try {
             var allLines = Files.readAllLines(path, StandardCharsets.UTF_8);
             int total = allLines.size();
@@ -86,7 +138,6 @@ public class FileReadTool implements Tool {
                 end = ((Number) input.get("line_end")).intValue();
             }
 
-            // 参数校验
             start = Math.max(1, start);
             end = Math.min(total, end);
 
@@ -94,12 +145,10 @@ public class FileReadTool implements Tool {
                 return "Error: line_start (" + start + ") > line_end (" + end + ")";
             }
 
-            // 限制行数
             if (end - start + 1 > MAX_LINES) {
                 end = start + MAX_LINES - 1;
             }
 
-            // 构建带行号的输出
             StringBuilder sb = new StringBuilder();
             for (int i = start - 1; i < end; i++) {
                 sb.append(String.format("%4d | %s%n", i + 1, allLines.get(i)));
@@ -116,8 +165,49 @@ public class FileReadTool implements Tool {
         }
     }
 
+    /**
+     * 获取文件扩展名（小写，不含点）。
+     */
+    private String getExtension(String filename) {
+        int dot = filename.lastIndexOf('.');
+        if (dot < 0 || dot == filename.length() - 1) return "";
+        return filename.substring(dot + 1).toLowerCase();
+    }
+
+    /**
+     * 根据扩展名返回 MIME 类型。
+     */
+    private String getMimeType(String ext) {
+        return switch (ext) {
+            case "png"  -> "image/png";
+            case "jpg", "jpeg" -> "image/jpeg";
+            case "gif"  -> "image/gif";
+            case "webp" -> "image/webp";
+            case "svg"  -> "image/svg+xml";
+            case "bmp"  -> "image/bmp";
+            case "ico"  -> "image/x-icon";
+            default     -> "application/octet-stream";
+        };
+    }
+
+    private String formatSize(long bytes) {
+        if (bytes < 1024) return bytes + " B";
+        if (bytes < 1024 * 1024) return String.format("%.1f KB", bytes / 1024.0);
+        return String.format("%.1f MB", bytes / (1024.0 * 1024));
+    }
+
+    private String escapeJson(String s) {
+        if (s == null) return "";
+        return s.replace("\\", "\\\\").replace("\"", "\\\"").replace("\n", "\\n");
+    }
+
     @Override
     public String activityDescription(Map<String, Object> input) {
-        return "📄 Reading " + input.getOrDefault("file_path", "file");
+        String fp = (String) input.getOrDefault("file_path", "file");
+        String ext = getExtension(fp);
+        if (IMAGE_EXTENSIONS.contains(ext)) {
+            return "🖼️ Reading image " + fp;
+        }
+        return "📄 Reading " + fp;
     }
 }