fix: correct operator names, connection types, and implement __patch_find_replace (#665, #659, #642) (#672)

Three critical fixes in n8n_update_partial_workflow:

- **#665**: Replace incorrect `isNotEmpty`/`isEmpty` operator names with `notEmpty`/`empty`
  across validators, sanitizer, docs, and error messages. Add auto-correction in sanitizer.
  Unknown operators silently returned false in n8n's execution engine.

- **#659**: Remap numeric `targetInput` values (e.g., "0") to "main" in addConnection.
  Relax sourceOutput remapping guard for redundant sourceOutput+sourceIndex combinations.
  Also resolves #653 (dangling connections caused by malformed type:"0" connections).

- **#642**: Implement __patch_find_replace for surgical string edits in updateNode.
  Previously stored patch objects literally as jsCode, producing [object Object].
  Now reads current value, applies find/replace sequentially, writes back the string.

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/integration/validation/real-world-structure-validation.test.ts

@@ -445,7 +445,7 @@ describe('Integration: Real-World Type Structure Validation', () => {
     expect(sheetIdErrors).toBe(0);
   });
 
-  it('should validate all filter operations including exists/notExists/isNotEmpty', async () => {
+  it('should validate all filter operations including exists/notExists/notEmpty', async () => {
     const templates = db.prepare(`
       SELECT id, name, workflow_json_compressed
       FROM templates