fix: enforce ALLOWED_ROOT_DIRECTORY path validation across all routes

This fixes a critical security issue where path parameters from client requests
were not validated against ALLOWED_ROOT_DIRECTORY, allowing attackers to access
files and directories outside the configured root directory.

Changes:
- Add validatePath() checks to 29 route handlers that accept path parameters
- Validate paths in agent routes (workingDirectory, imagePaths)
- Validate paths in feature routes (projectPath)
- Validate paths in worktree routes (projectPath, worktreePath)
- Validate paths in git routes (projectPath, filePath)
- Validate paths in auto-mode routes (projectPath, worktreePath)
- Validate paths in settings/suggestions routes (projectPath)
- Return 403 Forbidden for paths outside ALLOWED_ROOT_DIRECTORY
- Maintain backward compatibility (unrestricted when env var not set)

Security Impact:
- Prevents directory traversal attacks
- Prevents unauthorized file access
- Prevents arbitrary code execution via unvalidated paths

All validation follows the existing pattern in fs routes and session creation,
using the validatePath() function from lib/security.ts which checks against
both ALLOWED_ROOT_DIRECTORY and DATA_DIR (appData).

Tests: All 653 unit tests passing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

apps/server/src/routes/git/routes/diffs.ts

@@ -5,6 +5,7 @@
 import type { Request, Response } from "express";
 import { getErrorMessage, logError } from "../common.js";
 import { getGitRepositoryDiffs } from "../../common.js";
+import { validatePath, PathNotAllowedError } from "../../../lib/security.js";
 
 export function createDiffsHandler() {
   return async (req: Request, res: Response): Promise<void> => {
@@ -16,6 +17,20 @@ export function createDiffsHandler() {
         return;
       }
 
+      // Validate paths are within ALLOWED_ROOT_DIRECTORY
+      try {
+        validatePath(projectPath);
+      } catch (error) {
+        if (error instanceof PathNotAllowedError) {
+          res.status(403).json({
+            success: false,
+            error: error.message,
+          });
+          return;
+        }
+        throw error;
+      }
+
       try {
         const result = await getGitRepositoryDiffs(projectPath);
         res.json({

apps/server/src/routes/git/routes/file-diff.ts

@@ -7,6 +7,7 @@ import { exec } from "child_process";
 import { promisify } from "util";
 import { getErrorMessage, logError } from "../common.js";
 import { generateSyntheticDiffForNewFile } from "../../common.js";
+import { validatePath, PathNotAllowedError } from "../../../lib/security.js";
 
 const execAsync = promisify(exec);
 
@@ -25,6 +26,21 @@ export function createFileDiffHandler() {
         return;
       }
 
+      // Validate paths are within ALLOWED_ROOT_DIRECTORY
+      try {
+        validatePath(projectPath);
+        validatePath(filePath);
+      } catch (error) {
+        if (error instanceof PathNotAllowedError) {
+          res.status(403).json({
+            success: false,
+            error: error.message,
+          });
+          return;
+        }
+        throw error;
+      }
+
       try {
         // First check if the file is untracked
         const { stdout: status } = await execAsync(