feat(validator): detect conditional branch fan-out & connection auto-fixes (#622)

* feat(auto-fixer): add 5 connection structure fix types

Add automatic repair for malformed workflow connections commonly
generated by AI models:
- connection-numeric-keys: "0","1" keys → main[0], main[1]
- connection-invalid-type: type:"0" → type:"main" (or parent key)
- connection-id-to-name: node ID refs → node name refs
- connection-duplicate-removal: dedup identical connection entries
- connection-input-index: out-of-bounds input index → clamped

Includes collision-safe ID-to-name renames, medium confidence on
merge conflicts and index clamping, shared CONNECTION_FIX_TYPES
constant, and 24 unit tests.

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


* feat(validator): detect IF/Switch/Filter conditional branch fan-out misuse

Add CONDITIONAL_BRANCH_FANOUT warning when conditional nodes have all
connections on main[0] with higher outputs empty, indicating both
branches execute together instead of being split by condition.

Extract getShortNodeType() and getConditionalOutputInfo() helpers to
deduplicate conditional node detection logic.

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

src/mcp/handlers-n8n-manager.ts

@@ -424,7 +424,13 @@ const autofixWorkflowSchema = z.object({
     'node-type-correction',
     'webhook-missing-path',
     'typeversion-upgrade',
-    'version-migration'
+    'version-migration',
+    'tool-variant-correction',
+    'connection-numeric-keys',
+    'connection-invalid-type',
+    'connection-id-to-name',
+    'connection-duplicate-removal',
+    'connection-input-index'
   ])).optional(),
   confidenceThreshold: z.enum(['high', 'medium', 'low']).optional().default('medium'),
   maxFixes: z.number().optional().default(50)

src/mcp/tools-n8n-manager.ts

@@ -284,7 +284,7 @@ export const n8nManagementTools: ToolDefinition[] = [
   },
   {
     name: 'n8n_autofix_workflow',
-    description: `Automatically fix common workflow validation errors. Preview fixes or apply them. Fixes expression format, typeVersion, error output config, webhook paths.`,
+    description: `Automatically fix common workflow validation errors. Preview fixes or apply them. Fixes expression format, typeVersion, error output config, webhook paths, connection structure issues (numeric keys, invalid types, ID-to-name, duplicates, out-of-bounds indices).`,
     inputSchema: {
       type: 'object',
       properties: {
@@ -301,7 +301,7 @@ export const n8nManagementTools: ToolDefinition[] = [
           description: 'Types of fixes to apply (default: all)',
           items: {
             type: 'string',
-            enum: ['expression-format', 'typeversion-correction', 'error-output-config', 'node-type-correction', 'webhook-missing-path', 'typeversion-upgrade', 'version-migration']
+            enum: ['expression-format', 'typeversion-correction', 'error-output-config', 'node-type-correction', 'webhook-missing-path', 'typeversion-upgrade', 'version-migration', 'tool-variant-correction', 'connection-numeric-keys', 'connection-invalid-type', 'connection-id-to-name', 'connection-duplicate-removal', 'connection-input-index']
           }
         },
         confidenceThreshold: {