feat: add project list scrolling and compact prompt path

[skulidropek]

Summary

• add viewport-based scrolling window for project selection list in TUI
• show scroll hints when entries are hidden above/below
• shorten prompt path segments for bash and zsh (e.g. ~/d/n/@changesets)
• add tests for list window calculation and prompt template output

Closes #66
Closes #58

Verification

• pnpm --filter ./packages/app lint
• pnpm --filter ./packages/lib lint
• pnpm --filter ./packages/app exec vitest run tests/docker-git/menu-select-order.test.ts tests/docker-git/menu-select-connect.test.ts
• pnpm --filter ./packages/docker-git test -- tests/core/templates.test.ts