feat(cli): add vibeprompt CLI and interactive TUI (closes #19)

cli/.gitignore

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+node_modules/
+dist/

cli/README.md

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+# vibeprompt CLI
+
+Browse, search, copy, and run vibeprompt prompts from your terminal.
+
+## Install
+
+```bash
+npm install -g ./cli   # from the repo root, or after publishing:
+npm install -g vibeprompt
+```
+
+## Usage
+
+```bash
+vibeprompt                     # alias for browse
+vibeprompt browse              # list all categories
+vibeprompt browse "Agent Setup"  # list prompts in a category
+vibeprompt search "tdd"        # full-text search across all prompts
+vibeprompt show <slug>         # print a prompt to stdout
+vibeprompt show "AGENTS.md Generator"  # fuzzy: works with a title too
+vibeprompt copy <slug>         # copy a prompt to the clipboard
+vibeprompt workflow            # show the 9-step playbook
+vibeprompt tui                 # open the interactive terminal UI
+```
+
+The TUI supports arrow keys to move, Enter to open a prompt detail pane,
+`s` to search, `c` to cycle categories, and `Esc` to back out or quit.
+
+## How it works
+
+The CLI reads prompts straight from the `prompt-library/` folder. It finds it
+by walking up from the current directory, or you can point at it explicitly:
+
+```bash
+VIBEPROMPT_ROOT=/path/to/vibe-prompt/prompt-library vibeprompt browse
+```
+
+## Development
+
+```bash
+npm install
+npm run dev -- tui # run the TUI from source (no build step)
+npm run build      # tsup -> dist/
+npm run typecheck  # tsc --noEmit
+npm test           # build + run the CLI/TUI test suite
+```
+
+> `npm run dev` without the `tui` argument runs the default `browse` command
+> and just prints the category list. Pass `tui` to get the interactive UI.