refactor(#82): remove dead SkeletonList/SkeletonCard composables

* ci: prevent concurrency cancellation on rapid main merges

The concurrency group used github.ref which is static for main
(refs/heads/main). When multiple PRs merged rapidly (~2 min apart),
each merge commit cancelled the previous CI run before it could finish.

Fix: use github.sha for push events to main (unique per commit) while
keeping the ref-based group for PR branches (cancels on new commits to
the same PR branch).

* refactor(#82): remove dead SkeletonList/SkeletonCard composables

---------

Co-authored-by: ronia <ronia@m57>
Co-authored-by: M57 <hy4ri@users.noreply.github.com>

AGENTS.md

@@ -105,14 +105,13 @@ status colors (success/warning/error/info) are ALWAYS brand-defined via
 git checkout main && git pull origin main
 git checkout -b fix/issue-N-description    # or feat/...
 # make changes, run ./ktlint --format
-git -c user.name='ronia' -c user.email='ronia@m57' commit -m "fix(#N): description"
+git commit -m "fix(#N): description"
 git push -u origin HEAD
 gh pr create --title "fix(#N): description" --body "Closes #N"
 ```
 
 ### Commit Conventions
 
-- **Author:** `ronia@m57` (set via `-c user.name` / `-c user.email`).
 - **NO co-author trailer.** No `Co-Authored-By`, no `Generated with ...`. Ever.
 - **Short commits:** subject line + max 2 lines of body. Split into atomic commits
   rather than writing long bodies.