spawn_dev.py's --model has no default, and claude's own default resolves to Opus here nf-y3rt ← Beads

Twinned from https://github.com/cfsh/ninefold/issues/979 by tools/beads/import_github.py's reconcile pass.

Per Aedan's standing instruction (2026-08-10, "let's just try sonnet for all issues except really heavy lifting design work"), every ordinary dev spawn should run Sonnet unless the CTO deliberately overrides it. \--model\ has no default in the parser, and omitting it does not mean Sonnet — it means whatever \claude\ itself defaults to, which on this box is Opus. Confirmed live: \nf-dev-reap-standing-file\ (spawned just now, no \--model\ passed) came up on \claude-opus-5\ per its transcript's \"model"\ field.

Default \--model\ to Sonnet when omitted, for every mode (\--standing-slot\, \--resume\, \--adopt\, plain spawn) — an explicit \--model\ should still override it.