fix: automatically sanitize forbidden characters in task titles

- Remove validation that rejects tasks with forbidden filename characters
- Allow automatic sanitization via existing sanitizeForFilename() function
- Remove "invalid characters" error message from instant task convert
- Enable previously skipped test for invalid characters handling
- Fixes inconsistent behavior between instant convert and manual creation

Fixes #590, Fixes #436

src/services/InstantTaskConvertService.ts

@@ -238,8 +238,6 @@ export class InstantTaskConvertService {
             console.error('Error during instant task conversion:', error);
             if (error.message.includes('file already exists')) {
                 new Notice('A file with this name already exists. Please try again or rename the task.');
-            } else if (error.message.includes('invalid characters')) {
-                new Notice('Task title contains invalid characters for filename.');
             } else {
                 new Notice('Failed to convert task. Please try again.');
             }
@@ -323,18 +321,6 @@ export class InstantTaskConvertService {
             return { isValid: false, error: 'Task title cannot be empty.' };
         }
 
-
-        // Validate against dangerous characters for file operations
-        const basicDangerousChars = /[<>:"/\\|?*]/;
-        const hasControlChars = parsedData.title.split('').some(char => {
-            const code = char.charCodeAt(0);
-            return code <= 31 || code === 127;
-        });
-        
-        if (basicDangerousChars.test(parsedData.title) || hasControlChars) {
-            return { isValid: false, error: 'Task title contains invalid characters for file operations.' };
-        }
-
         // Validate date formats if present
         const dateFields = ['dueDate', 'scheduledDate', 'startDate', 'createdDate', 'doneDate'];
         for (const field of dateFields) {

tests/integration/task-creation-workflow.test.ts

@@ -452,9 +452,7 @@ describe('Task Creation Workflow Integration', () => {
       expect(result.cacheUpdated).toBe(false);
     });
 
-    it.skip('should handle invalid characters in task titles', async () => {
-      // TODO: This test has test isolation issues - passes individually but fails in suite
-      // The functionality works correctly, but the test environment has mock pollution
+    it('should handle invalid characters in task titles', async () => {
       const taskData = {
         title: 'Task with invalid chars: <>:"|?*\\/[]'
       };