Feature Request: Improve "Install Missing Custom Nodes" Detection and Feedback

# Feature Request: Improve "Install Missing Custom Nodes" Detection and Feedback

## Problem

When opening a workflow that depends on a custom node pack which is not present in the ComfyUI-Manager registry (for example, **Dream Video Batches**), the **Install Missing Custom Nodes** feature does not detect it.

From a user's perspective, this is confusing because there is no indication whether:

* the node pack is unavailable,
* the workflow is outdated,
* the node names have changed, or
* the node pack simply isn't included in the registry.

The result is that users often have to manually search GitHub or ask the community to identify the missing repository.

## Expected Behavior

If a missing node cannot be mapped to a registered node pack, ComfyUI-Manager could provide clearer feedback instead of silently omitting it.

For example:

> "Some missing nodes could not be matched to a known custom node pack. They may require manual installation."

or

> "This workflow contains nodes that are not currently available in the ComfyUI-Manager registry."

## Possible Improvements

* Increase registry coverage for commonly used custom node packs.
* Allow community-contributed mappings for missing node packs.
* Display unmatched node names so users know exactly what is missing.
* Offer a fallback search (e.g. GitHub or registry search) using the missing node names.
* Clearly distinguish between:

* missing because the node pack is not installed,
* missing because the node pack is not in the registry,
* missing because the workflow references obsolete node names.

## Why This Matters

The current behavior can make troubleshooting unnecessarily difficult, especially for newer users. When "Install Missing Custom Nodes" doesn't list a required node pack, it is easy to assume the workflow is broken or incompatible, when in reality the node pack simply requires manual installation.

Providing clearer feedback—or a fallback mechanism—would significantly improve the onboarding experience and reduce repetitive support questions.

Start at the “Install Missing Custom Nodes” workflow and trace how missing node names are detected, mapped to registry entries, and omitted when no match exists. Define the desired handling for unmatched nodes, including feedback and any fallback search, then verify the behavior with representative workflows such as one using Dream Video Batches.

Written by the indexing model from the issue text.