Modal that captures and persists an API key for one provider.
Dismissal values are members of AuthResult so callers in the recovery
path can distinguish "user just saved a key ā retry the failed
operation" from "user just cleared their key ā don't retry, that would
loop into the same error" from "user cancelled ā leave state alone".
Provider name (e.g., "anthropic").
Canonical env var the SDK reads, shown as helper text.
May be None for providers that don't use one of the
hardcoded env-var bindings (rare; the prompt still works).
Optional one-line context, e.g.,
"Required to use anthropic:claude-opus-4-7".
Compose the prompt.
Apply ASCII border when needed.
Validate, persist, and dismiss.
Dismiss without saving.
Open the delete-confirmation overlay for the stored credential.
