Add sensible overridable defaults to Artificer initialization

[BjRo]

Motivation

Testing Local Artificer with issue #217 required manually supplying the state path, repository and checkout, ticket scope, recurring authority, credential location, and installed delivery plugin roots before initialization. This is too much setup for the common local case when several values can be inferred from the current repository and host installation.

Acceptance criteria

• Common local initialization supplies sensible defaults for configuration that can be inferred safely from the current repository and host installation.
• Every default remains explicitly overridable.
• Recurring authority, permitted effects, ticket scope, and the confirmation that the account has no paid credit balance or automatic reload remain explicit rather than inferred.

Open questions

• Which initialization values can safely default, and which must remain explicit inputs?