Add persistent terminal aliases

[cursor]

Issue

Problem

The site is moving toward stronger terminal emulation, but the advertised alias command only printed a hard-coded stub (alias exit='close'). Visitors could not create real shortcuts, persist shell-like preferences, or remove them later.

Proposed improvement

Add persistent, shell-style aliases to the terminal runtime:

• alias h='history 3' creates a shortcut.
• h expands to the saved command, preserving extra arguments.
• alias lists built-in and custom aliases.
• unalias h removes a custom alias.
• Custom aliases persist in browser localStorage across reloads.
• Expansion detects recursive alias loops instead of hanging.

Acceptance criteria

• Users can create, list, execute, persist, and remove aliases from the terminal UI.
• Built-in aliases such as exit='close' remain read-only.
• Alias helpers have unit coverage for parsing, formatting, expansion, nested expansion, and loop detection.
• README documents the new terminal alias workflow.

Implementation

• Added alias helper functions in src/lib/terminal/index.js.
• Wired alias state and expansion into src/scripts/terminal.js, including pipeline support.
• Added the unalias command to command lists, help output, and man-page metadata.
• Documented usage examples in README.md.

Testing

• Pre-push hook ran npm run check successfully:
  • ESLint passed.
  • Prettier format check passed.
  • Vitest coverage passed: 2 test files, 69 tests.
  • Astro production build passed.
• Manual browser walkthrough recorded and reviewed: create alias, execute it, reload to verify persistence, list aliases, remove alias, confirm removed alias is no longer found.