Add Ctrl+R reverse history search to terminal

[cursor]

Summary

• Adds Bash-style Ctrl+R reverse command history search to the portfolio terminal.
• Adds a tested searchCommandHistory helper for newest-to-oldest matching, cycling, and wraparound.
• Updates terminal hints, history manual text, and README shortcut docs.

New Issue Description

Problem

The site aims to feel like a terminal emulator, but command history only supported Up/Down navigation. Users could not quickly search previous commands by substring, which is a common shell workflow.

Proposed Improvement

Implement Ctrl+R reverse history search:

• Ctrl+R enters reverse search mode.
• Typing narrows matches case-insensitively.
• Repeated Ctrl+R cycles older matching commands and wraps.
• Enter executes the selected command.
• Esc, Ctrl+C, or Ctrl+G cancels and restores the original input.

Acceptance Criteria

• Users can recall and execute a previous command via Ctrl+R without touching Up/Down history navigation.
• Search behavior is covered by unit tests for matching, cycling, wraparound, and no-match cases.
• The shortcut is discoverable in onboarding hints, man history, and README docs.

Validation

• pnpm check passed via the pre-push hook: lint, Prettier check, Vitest coverage (69 tests), and Astro build.
• Manual browser walkthrough recorded: /opt/cursor/artifacts/ctrl_r_reverse_history_search_walkthrough.mp4.