#1563 Improve multi-word search query handling and guidance

The CLI rejected a valid natural-language search attempt because multi-word queries must be quoted at the shell boundary.

Steps to reproduce:

1. Run: swamp extension search home assistant --json
2. Observe: Too many arguments: assistant
3. Run: swamp extension search "home assistant" --json
4. The quoted form succeeds.

Expected behavior:

• Multi-word search input should either be accepted as one query by the CLI, or the command help/error should clearly explain that the query must be shell-quoted.
• Agent-facing examples and guidance should consistently show quoting for queries containing spaces.

Environment:

• Swamp 20260808.215448.0-sha.68363cc0
• Linux

This was encountered while searching the extension registry for a Home Assistant integration.