add idempotentHint to safe-to-retry vCenter tools

Mark tools that handle already-in-target-state gracefully:
- storage_vmotion: returns "no_migration_needed" if already on target
- convert_to_template: returns "already_template" if already converted
- convert_to_vm: returns "already_vm" if already a VM

This signals to LLM clients that these operations are safe to retry.

src/esxi_mcp_server/mixins/vcenter_ops.py

@@ -23,8 +23,8 @@ class VCenterOpsMixin(MCPMixin):
 
     @mcp_tool(
         name="storage_vmotion",
-        description="Move a VM's disks to a different datastore (Storage vMotion)",
+        description="Move a VM's disks to a different datastore (Storage vMotion). Idempotent if already on target.",
-        annotations=ToolAnnotations(destructiveHint=True),
+        annotations=ToolAnnotations(destructiveHint=True, idempotentHint=True),
     )
     def storage_vmotion(
         self,
@@ -161,8 +161,8 @@ class VCenterOpsMixin(MCPMixin):
 
     @mcp_tool(
         name="convert_to_template",
-        description="Convert a VM to a template",
+        description="Convert a VM to a template (idempotent - safe to call on existing template)",
-        annotations=ToolAnnotations(destructiveHint=True),
+        annotations=ToolAnnotations(destructiveHint=True, idempotentHint=True),
     )
     def convert_to_template(self, vm_name: str) -> dict[str, Any]:
         """Convert a VM to a template.
@@ -200,8 +200,8 @@ class VCenterOpsMixin(MCPMixin):
 
     @mcp_tool(
         name="convert_to_vm",
-        description="Convert a template back to a VM",
+        description="Convert a template back to a VM (idempotent - safe to call on existing VM)",
-        annotations=ToolAnnotations(destructiveHint=True),
+        annotations=ToolAnnotations(destructiveHint=True, idempotentHint=True),
     )
     def convert_to_vm(
         self,