Add shell tab completion scripts for zsh and bash

[KryptosAI]

Summary

Add shell tab completion for zsh and bash so users can autocomplete commands, flags, and server names when using the CLI.

Files to modify

• scripts/completions/_mcp-observatory (new zsh completion script)
• scripts/completions/mcp-observatory.bash (new bash completion script)
• package.json — add a postinstall script hint or note in README about sourcing completions

What to change

1. Create a zsh completion file at scripts/completions/_mcp-observatory that:
   • Autocompletes top-level commands: test, scan, report, history, setup-ci, demo
   • Autocompletes flags: --json, --watch, --accessible, --quiet, --timeout, etc.
   • Autocompletes --format values: json, markdown, terminal, html
2. Create a bash completion file at scripts/completions/mcp-observatory.bash with the same completions.
3. Add a note to the README installation section:

   # zsh
   source <(mcp-observatory completion zsh)
   # bash
   source <(mcp-observatory completion bash)

4. Follow the existing command definitions in src/commands/ to ensure all flags and subcommands are covered.

Reference

Use existing CLI command definitions in src/commands/*.ts for flag names. See similar completions in projects like gh or kubectl for patterns.

Estimated time

~20 minutes