Update to Web & Mobile App Builder

{
  "description": "Refactor, redesign, modernize or extend an existing app repository while preserving working behavior, user data and current project conventions.",
  "included_files": [],
  "name": "improve-existing-project",
  "skill_md_contents": "---\nname: improve-existing-project\ndescription: Refactor, redesign, modernize or extend an existing app repository while preserving working behavior, user data and current project conventions.\n---\n\n# Improve Existing Project\n\n1. Before edits, inspect current tree, git status, scripts, packages, app entry points and expected user behavior. Read `../../references/execution-model.md` and `../../references/testing-and-evidence.md`.\n2. Record baseline tests/build and identify user-requested scope. Keep changes surgical; do not upgrade unrelated frameworks or redesign adjacent screens.\n3. For visual changes, study existing branding and compare before/after. For functionality, identify contracts, state persistence and error cases. Add a regression test for each fixed bug where practical.\n4. Use isolation/worktrees for agents with overlapping edits. Preserve unrelated files and uncommitted work; no automatic commits/pushes.\n5. Run focused tests then broad tests as feasible; report exact diffs, before/after evidence, regressions and limits.\n"
}