fix: resolve multiple n8n_update_partial_workflow bugs (#635)

* fix: use correct MCP SDK API for server capabilities in test

getServerVersion() returns Implementation (name/version only), not the
full init result. Use client.getServerCapabilities() instead to access
server capabilities, fixing the CI typecheck failure.

Concieved by Romuald Członkowski - www.aiadvisors.pl/en

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

* fix: resolve multiple n8n_update_partial_workflow bugs (#592, #599, #610, #623, #624, #625, #629, #630, #633)

Phase 1 - Data loss prevention:
- Add missing unary operators (empty, notEmpty, exists, notExists) to sanitizer (#592)
- Preserve positional empty arrays in connections during removeNode/cleanStale (#610)
- Scope sanitization to modified nodes only, preventing unrelated node corruption
- Add empty body {} to activate/deactivate POST calls to fix 415 errors (#633)

Phase 2 - Error handling & response clarity:
- Serialize Zod errors to readable "path: message" strings (#630)
- Add saved:true/false field to all response paths (#625)
- Improve updateNode error hint with correct structure example (#623)
- Track removed node names for better removeConnection errors (#624)

Phase 3 - Connection & type fixes:
- Coerce sourceOutput/targetInput to String() consistently (#629)
- Accept numeric sourceOutput/targetInput at Zod schema level via transform

Phase 4 - Tag operations via dedicated API (#599):
- Track tags as tagsToAdd/tagsToRemove instead of mutating workflow.tags
- Orchestrate tag creation and association via listTags/createTag/updateWorkflowTags
- Reconcile conflicting add/remove for same tag (last operation wins)
- Tag failures produce warnings, not hard errors

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

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

* docs: add v2.37.0 changelog entry

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

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

* fix: resolve pre-existing integration test failures in CI

- Create new MCP Server instance per connection in test helpers (SDK 1.27+
  requires separate Protocol instance per connection)
- Normalize database paths with path.resolve() in shared-database singleton
  to prevent path mismatch errors across test files
- Add no-op catch handler to deferred initialization promise in server.ts
  to prevent unhandled rejection warnings
- Properly call mcpServer.shutdown() in test helper close() to release
  shared database references

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

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

---------

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

src/services/node-sanitizer.ts

@@ -41,7 +41,7 @@ export function sanitizeWorkflowNodes(workflow: any): any {
 
   return {
     ...workflow,
-    nodes: workflow.nodes.map((node: any) => sanitizeNode(node))
+    nodes: workflow.nodes.map(sanitizeNode)
   };
 }
 
@@ -121,9 +121,7 @@ function sanitizeFilterConditions(conditions: any): any {
 
   // Sanitize conditions array
   if (sanitized.conditions && Array.isArray(sanitized.conditions)) {
-    sanitized.conditions = sanitized.conditions.map((condition: any) =>
-      sanitizeCondition(condition)
-    );
+    sanitized.conditions = sanitized.conditions.map(sanitizeCondition);
   }
 
   return sanitized;
@@ -214,18 +212,25 @@ function inferDataType(operation: string): string {
     return 'boolean';
   }
 
-  // Number operations
+  // Number operations (partial match to catch variants like "greaterThan" containing "gt")
   const numberOps = ['isNumeric', 'gt', 'gte', 'lt', 'lte'];
   if (numberOps.some(op => operation.includes(op))) {
     return 'number';
   }
 
-  // Date operations
+  // Date operations (partial match to catch variants like "isAfter" containing "after")
   const dateOps = ['after', 'before', 'afterDate', 'beforeDate'];
   if (dateOps.some(op => operation.includes(op))) {
     return 'dateTime';
   }
 
+  // Object operations: empty/notEmpty/exists/notExists are generic object-level checks
+  // (distinct from isEmpty/isNotEmpty which are boolean-typed operations)
+  const objectOps = ['empty', 'notEmpty', 'exists', 'notExists'];
+  if (objectOps.includes(operation)) {
+    return 'object';
+  }
+
   // Default to string
   return 'string';
 }
@@ -239,7 +244,11 @@ function isUnaryOperator(operation: string): boolean {
     'isNotEmpty',
     'true',
     'false',
-    'isNumeric'
+    'isNumeric',
+    'empty',
+    'notEmpty',
+    'exists',
+    'notExists'
   ];
   return unaryOps.includes(operation);
 }