#3014 Docs: vault create and vault migrate name missing required --config fields and prompt for them

What changed

swamp-club#3003 changes how swamp vault create <type> <name> and swamp vault migrate <vault> --to-type <type> behave when the target vault type has required config fields that --config does not supply:

• The error names each missing required field with its description from the type's schema and shows an example --config to re-run with, instead of printing the raw schema validation output. Wrong-typed fields and unknown keys are explained the same way.
• When the type is not installed yet, the check runs against the registry's published field list before the extension is installed.
• In a terminal (log output, no --json, no --yes, no --server) the command prompts for each missing required string field instead of failing.

Which manual page

content/manual/reference/vaults.md: the --config rows in the swamp vault create and swamp vault migrate option tables, and the migrate section.

Suggested content

Under each command's --config description, add a sentence like: "If the type requires fields that --config does not provide, the command names them and shows an example; in an interactive terminal it prompts for each missing string field. Use --json or --yes to fail instead of prompting." Optionally show the new error output for @swamp/1password without --config as an example.