Node replacement ignores DynamicCombo child mappings with dot notation

### Prerequisites

- [x] I am running the latest version of ComfyUI
- [x] I have custom nodes enabled

### What happened?

When replacing a missing node using NodeReplace, mappings that target DynamicCombo child fields (dot notation) are not applied.

Example mappings like:
- {"new_id": "operation.operand_a", "old_id": "mode_settings.value_a"}
- {"new_id": "operation.operand_b", "old_id": "mode_settings.value_b"}
do not transfer values, even though the replacement is otherwise executed (node is replaced, non-nested mappings may work, outputs may remap).

This appears inconsistent with docs/core examples that use dot notation for complex inputs (e.g. resize_type.multiplier).
Mapping between two nodes with DynamicCombo that has different child widget count also seem to not work as expected.

### Steps to Reproduce

**1. Create an old node with a mode widget + numeric widgets (or old DynamicCombo fields), e.g.:**

- mode_settings
- mode_settings.value_a
- mode_settings.value_b

**2. Create a new node using io.DynamicCombo.Input("operation", ...) with child fields:**

- operation.operand_a
- operation.operand_b

**3. Register a replacement with dot-notation child mappings, e.g.:**

- operation <- mode_settings
- operation.operand_a <- mode_settings.value_a
- operation.operand_b <- mode_settings.value_b

**4. Load a workflow containing the old node as missing, then click Replace.**

**5. Observe the replaced node:**

- parent mode may transfer
- child fields (operand_a, operand_b) remain defaults instead of transferred values.

### How is this affecting you?

Feature doesn't work as expected

### ComfyUI Frontend Version

1.42.10

### Browser

Chrome/Chromium

### Console Errors

```javascript

```

### Logs

```shell

```

### Additional Context

_No response_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-11185-Node-replacement-ignores-DynamicCombo-child-mappings-with-dot-notation-3416d73d365081a591cbf17ae688a65e) by [Unito](https://www.unito.io)

Start at the NodeReplace replacement-mapping logic and trace how DynamicCombo inputs and dot-notation child fields are handled. Reproduce the workflow with operation.operand_a/operand_b mapped from mode_settings.value_a/value_b; done means the parent and child values transfer correctly, including when the DynamicCombo child counts differ.

Written by the indexing model from the issue text.