Layers that change same files make dive unusably slow

[huntharo]

What happened:

1. Reproducible public image test case: dive ghcr.io/openclaw/openclaw:2026.2.17
2. Opening this takes minutes on a MacBook Pro M2 Max
3. Once open, each down arrow to move to another layer (even the ones in the base image that have no problems) takes 5-15 seconds - CPU shoots up to 500% during this time

What you expected to happen:

Not take minutes and not use 500% CPU when pressing the arrow keys OR at least isolate the slowness to when the operation involves a layer that repeats tens of thousands of files in another layer.

How to reproduce it (as minimally and precisely as possible):

1. Problem case: dive ghcr.io/openclaw/openclaw:2026.2.17
2. Problem layer removed (the chown layer that duplicates the 900 MB): dive ghcr.io/openclaw/openclaw:2026.2.21

When the problem layer is not present dive starts quickly and responds immediately to selecting different layers with the arrow keys, with no 500% CPU spike (or at least, so short as to not be noticable).

Anything else we need to know?:

While this may seem like a duplicate report... this is a specific case that is reproducible and will likely lead to being able to find the problem and fix it. I'm going to make an attempt at fixing this now.

Environment:

• OS version: macOS 26.2
• Docker version (if applicable): Engine 29.2.1

[huntharo]

Fix in hand