fix+test: code quality improvements + 87 unit tests

Fixes:
- Resource leaks: process cleanup in BashTool, GrepTool, NotificationService
- Input validation: null/blank checks in BashTool, FileEditTool, GrepTool
- Path traversal: FileEditTool blocks ../ escape from workDir
- Thread safety: AgentLoop messageHistory now synchronizedList
- Error handling: log instead of silently swallow exceptions
- Bounds validation: RateLimiter constructor validates all params

Tests (87 total):
- TokenEstimationServiceTest: 14 tests (estimation, cost, formatting)
- RateLimiterTest: 12 tests (limits, cooldown, reset, concurrent)
- InternalLoggerTest: 12 tests (levels, structured, file output, export)
- NotificationServiceTest: 6 tests (config, disabled mode)
- FileEditToolTest: 8 tests (validation, traversal, core edit)
- BashToolTest: 9 tests (validation, dangerous commands, metadata)
- GrepToolTest: 5 tests (validation, metadata)
- Phase4CommandsTest: 21 tests (all Phase 4B+4D command metadata)

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

src/main/java/com/claudecode/core/AgentLoop.java

@@ -73,7 +73,7 @@ public class AgentLoop {
     private volatile boolean cancelled = false;
 
     /** 消息历史 —— 自行管理，不依赖 Spring AI ChatMemory */
-    private final List<Message> messageHistory = new ArrayList<>();
+    private final List<Message> messageHistory = java.util.Collections.synchronizedList(new ArrayList<>());
 
     /** 工具调用事件回调：在每次工具调用前/后通知 UI */
     private Consumer<ToolEvent> onToolEvent;
@@ -371,7 +371,9 @@ public class AgentLoop {
             Map<String, Object> parsedArgs = Map.of();
             try {
                 parsedArgs = MAPPER.readValue(toolArgs, Map.class);
-            } catch (Exception ignored) {}
+            } catch (Exception e) {
+                log.debug("Failed to parse tool arguments for {}: {}", toolName, e.getMessage());
+            }
 
             // PreToolUse Hook
             var preHookCtx = new HookManager.HookContext(toolName, parsedArgs);

src/main/java/com/claudecode/core/NotificationService.java

@@ -116,16 +116,19 @@ public class NotificationService {
                 "$n.ShowBalloonTip(3000,'%s','%s','Info');" +
                 "Start-Sleep 1;$n.Dispose()",
                 escape(title), escape(message));
-        new ProcessBuilder("powershell", "-NoProfile", "-Command", ps)
+        Process p = new ProcessBuilder("powershell", "-NoProfile", "-Command", ps)
                 .redirectErrorStream(true).start();
+        // Don't block, but schedule cleanup
+        p.onExit().thenRun(p::destroyForcibly);
     }
 
     private void sendMac(String title, String message) throws IOException {
         String script = String.format(
                 "display notification \"%s\" with title \"%s\"",
                 escape(message), escape(title));
-        new ProcessBuilder("osascript", "-e", script)
+        Process p = new ProcessBuilder("osascript", "-e", script)
                 .redirectErrorStream(true).start();
+        p.onExit().thenRun(p::destroyForcibly);
     }
 
     private void sendLinux(String title, String message, String level) throws IOException {
@@ -134,8 +137,9 @@ public class NotificationService {
             case "warning" -> "normal";
             default -> "low";
         };
-        new ProcessBuilder("notify-send", "-u", urgency, title, message)
+        Process p = new ProcessBuilder("notify-send", "-u", urgency, title, message)
                 .redirectErrorStream(true).start();
+        p.onExit().thenRun(p::destroyForcibly);
     }
 
     private String escape(String s) {

src/main/java/com/claudecode/core/RateLimiter.java

@@ -62,6 +62,15 @@ public class RateLimiter {
      * @param maxConcurrent        最大并发执行数
      */
     public RateLimiter(int maxRequestsPerWindow, Duration windowDuration, int maxConcurrent) {
+        if (maxRequestsPerWindow <= 0) {
+            throw new IllegalArgumentException("maxRequestsPerWindow must be > 0, got: " + maxRequestsPerWindow);
+        }
+        if (windowDuration == null || windowDuration.isNegative() || windowDuration.isZero()) {
+            throw new IllegalArgumentException("windowDuration must be positive");
+        }
+        if (maxConcurrent <= 0) {
+            throw new IllegalArgumentException("maxConcurrent must be > 0, got: " + maxConcurrent);
+        }
         this.maxRequestsPerWindow = maxRequestsPerWindow;
         this.windowDuration = windowDuration;
         this.maxConcurrent = maxConcurrent;

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

@@ -151,9 +151,17 @@ public class BashTool implements Tool {
     @Override
     public String execute(Map<String, Object> input, ToolContext context) {
         String command = (String) input.get("command");
-        int timeout = input.containsKey("timeout")
-                ? ((Number) input.get("timeout")).intValue()
-                : DEFAULT_TIMEOUT;
+        if (command == null || command.isBlank()) {
+            return "Error: 'command' parameter is required and must not be empty.";
+        }
+        int timeout;
+        try {
+            timeout = input.containsKey("timeout")
+                    ? ((Number) input.get("timeout")).intValue()
+                    : DEFAULT_TIMEOUT;
+        } catch (ClassCastException e) {
+            timeout = DEFAULT_TIMEOUT;
+        }
         Path workDir = context.getWorkDir();
 
         // Sandbox check: block absolutely dangerous commands
@@ -261,14 +269,17 @@ public class BashTool implements Tool {
 
     /** 检查命令是否可用 */
     private static boolean isCommandAvailable(String... cmd) {
+        Process p = null;
         try {
-            Process p = new ProcessBuilder(cmd)
+            p = new ProcessBuilder(cmd)
                     .redirectErrorStream(true)
                     .start();
             p.getInputStream().readAllBytes();
             return p.waitFor(5, TimeUnit.SECONDS) && p.exitValue() == 0;
         } catch (Exception e) {
             return false;
+        } finally {
+            if (p != null) p.destroyForcibly();
         }
     }
 

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

@@ -68,8 +68,24 @@ public class FileEditTool implements Tool {
         String filePath = (String) input.get("file_path");
         String oldString = (String) input.get("old_string");
         String newString = (String) input.get("new_string");
+
+        if (filePath == null || filePath.isBlank()) {
+            return "Error: 'file_path' is required.";
+        }
+        if (oldString == null) {
+            return "Error: 'old_string' is required.";
+        }
+        if (newString == null) {
+            return "Error: 'new_string' is required.";
+        }
+
         Path path = context.getWorkDir().resolve(filePath).normalize();
 
+        // Path traversal protection
+        if (!path.startsWith(context.getWorkDir().normalize())) {
+            return "Error: Path traversal not allowed. Path must be within the working directory.";
+        }
+
         if (!Files.exists(path)) {
             return "Error: File not found: " + path;
         }

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

@@ -107,6 +107,9 @@ public class GrepTool implements Tool {
     @Override
     public String execute(Map<String, Object> input, ToolContext context) {
         String pattern = (String) input.get("pattern");
+        if (pattern == null || pattern.isBlank()) {
+            return "Error: 'pattern' parameter is required.";
+        }
         String searchPath = (String) input.getOrDefault("path", ".");
         String include = (String) input.getOrDefault("include", null);
         String type = (String) input.getOrDefault("type", null);
@@ -135,10 +138,12 @@ public class GrepTool implements Tool {
                 while ((line = reader.readLine()) != null && lines.size() < headLimit) {
                     lines.add(line);
                 }
+            } finally {
+                if (!process.waitFor(30, TimeUnit.SECONDS)) {
+                    process.destroyForcibly();
+                }
             }
 
-            process.waitFor(30, TimeUnit.SECONDS);
-
             if (lines.isEmpty()) {
                 return "No matches found for pattern: " + pattern;
             }