Add persistent terminal aliases

[cursor]

Issue

The terminal UI listed alias as a command, but it only printed a static placeholder and did not emulate real shell alias behavior. This limited the site's goal of becoming a richer terminal-emulation experience.

Improvement

Add persistent shell-style aliases that users can create, inspect, execute, and remove directly in the portfolio terminal.

Changes

• Added alias name='command', alias, alias <name>, unalias <name>, and unalias -a behavior backed by localStorage.
• Expanded aliases before command execution, including aliases used inside pipelines and aliases that preserve trailing arguments.
• Added alias-aware which output and tab completion.
• Documented alias emulation in README.md and built-in man alias / man unalias help.
• Added unit coverage for alias parsing, formatting, quoting, pipeline expansion, argument preservation, and loop detection.

Verification

• pnpm check passed during pre-push: lint, format check, coverage tests, and Astro build.
• Manual browser walkthrough passed on http://localhost:4321/: create/list/run aliases, alias pipeline (h | grep weather), which h, remove aliases, and confirm empty alias list.
• Walkthrough artifact: <video src="/artifacts/persistent_terminal_aliases_walkthrough.mp4" controls></video>