Complete post-publish steps for successful packages

[goulvenclech]

Related to #134

Describe the problem

When sampo publish fails partway through publishing multiple packages, post-publish steps (GitHub releases, tags) are not executed for packages that were successfully published.

Example scenario:

• Package A publishes successfully ✓
• Package B fails ✗
• Result: Package A is on the registry but has no GitHub release or tag 🙁

What's the expected result?

If a package publish fails, Sampo should:

• Skip remaining unpublished packages
• Still complete post-publish steps (GitHub releases, tags) for successfully published packages
• Report clear summary of what succeeded and what failed

Example output:

✓ Published package-a@1.0.0
✗ Failed to publish package-b@1.0.0: [error message]
⊘ Skipped package-c (depends on package-b)

Completing post-publish tasks for successful packages...
✓ Created tag package-a-v1.0.0
✓ Created GitHub release for package-a@1.0.0