Tasks

• Add a configure command (alias wizard) running the wizard by name, with no welcome and a non-interactive bail.
• Move the welcome onto the offer, and give it the configuration path that was looked for, the sample URL and the himalaya configure pointer.
• Add offer_configuration, raised by a bare himalaya and by account resolution, returning whether the wizard ran.
• Make account resolution a hook: drop the exit(0), re-read the configuration afterwards, and let the command fail the ordinary way when nothing landed.
• Guard both entry points on stdin().is_terminal() and printer.is_json().
• Resolve the target path from Config::target_path instead of prompting for it.
• Append to an existing configuration as plain text; suffix the account name until free; claim default only when no other account does.
• Name all three resolution failures: the path read, the accounts held, the two ways to pick a default.
• Report where the account landed, under which name, and what to run next.
• Tests: a generated account parses back, an appended one keeps the existing account and its comments, a taken name gets a suffix, a missing configuration constrains nothing.
• Build/test/fmt/clippy.
• Fold into cairn/spec/wizard.md; log; land.