fix: images clean matches registry tags, not capy prefix

[clean6378-max-it]

Closes #98

images clean --all used to drop anything that did not start with capy-ubuntu-, so generic-profile images like ubuntu-latest-gcc15:latest never got removed even when they were in image-registry.yml.
It now loads the registry (same resolution as list and build), intersects installed repo:tag strings with registry docker_tag values, and only removes those matches. --registry is available on clean for parity with the other images subcommands.

Tests cover generic and Capy tags, dry-run, empty intersection, cwd registry discovery, and a capy-prefixed orphan tag that the old prefix filter would have removed incorrectly.
Run pytest tests/test_images_paths.py -k clean or tag a stand-in image and try localci images clean --all --dry-run.

Summary by CodeRabbit

• New Features

  • Added optional registry-based filtering to localci images clean via --registry/-r.
  • When a registry is available, cleanup now removes only Docker tags present in both the local installation and the registry.

• Bug Fixes

  • Removed hardcoded tag filtering, improving which images are selected for cleanup.
  • Now reports “No localci images found.” when no local images match the registry.
  • Kept existing dry-run behavior to avoid Docker changes.

• Tests

  • Added regression coverage for the --all failure case when no registry can be resolved.

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📥 Commits

Reviewing files that changed from the base of the PR and between 2e7bdad and 9e826a0.

📒 Files selected for processing (1)

• cli/tests/test_images_paths.py

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📝 Walkthrough

Walkthrough

images clean now resolves an optional or discovered image-registry.yml, intersects its Docker tags with locally installed tags, and removes only matching images. Tests cover sorting, dry runs, registry discovery, no-op behavior, generic tags, and Capy tags.

Changes

Registry-driven image cleanup

Layer / File(s)	Summary
Registry-based cleanup selection cli/localci/cli/images.py	images clean accepts --registry/-r, loads the resolved registry, and selects matching installed tags through a sorted intersection instead of the capy-ubuntu- prefix.
Cleanup behavior validation cli/tests/test_images_paths.py	Tests verify deterministic target selection, explicit and discovered registries, dry-run behavior, no-op behavior, missing-registry errors, and cleanup of generic and Capy tags.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant User
  participant images_clean
  participant ImageRegistry
  participant Docker
  User->>images_clean: clean --all [--registry]
  images_clean->>ImageRegistry: resolve and load image-registry.yml
  ImageRegistry-->>images_clean: docker_tag values
  images_clean->>Docker: list installed tags
  images_clean->>Docker: remove matching tags
  Docker-->>images_clean: removal result

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Possibly related PRs

• cppalliance/local-ci-test-system#93: Introduced the registry path-resolution plumbing reused by images clean.

Suggested reviewers: wpak-ai, bradjin8

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 8.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: cleaning images by registry tags instead of a hardcoded capy prefix.
Linked Issues check	✅ Passed	The changes align with #98 by matching installed image tags against registry docker_tag values and adding the --registry option.
Out of Scope Changes check	✅ Passed	No unrelated or out-of-scope changes are evident from the summary; the edits stay within image cleanup and its tests.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/images-clean-registry-tags

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