Fetch run image locally for publish extensions

[TIR44]

Summary

• Fetched the run image into the Docker daemon when image extensions are used, even when --publish normally resolves it remotely.
• Forced the lifecycle extension run-image fetch path to use the daemon because it builds a local ephemeral run image from that base image.
• Added a regression test for --publish with Extensions.

Output

Before

pack build --publish --extension ... could validate the run image remotely, then fail later when the extension flow tried to create a local ephemeral run image from a base image that was not in the daemon.

After

The run image is available in the daemon before the extension flow creates the local ephemeral run image.

Documentation

• Should this change be documented?
  • No

Related

Resolves #2559

Tests

• go test ./pkg/client

GitHub checks passed on the latest commit (a4e1cec): DCO, CodeQL, build tests on macOS/Linux/Windows, and compatibility acceptance combos.

make unit failed locally because Docker is not available at /var/run/docker.sock; the changed pkg/client package passed during that run.