test(web): cover Squadron selection after draft auto-balancing #139

Add focused regression coverage for choosing a Squadron after an unscoped draft has already been auto-balanced. Fable's milestone 5B re-review found that explicit Squadron retargeting retains the upstream store's environmentSelection: "auto" and previous loadBalancedEnvironmentId. Current behavior is correct: the selected-Squadron guard excludes balancing, and the selector label derives from that guard. No production fix or extra store flag is requested.

Exercise two environments for one logical project: auto-balance the unscoped draft, choose a Squadron on the other environment through the existing chip, and verify its project, carrier, prompt and model survive subsequent balance results/rerenders without moving again. Include automatic and manual environment controls refusing to change that selected owner, while explicit Squadron retarget remains available. This should test observable behavior, not merely assert persisted fields or callback wiring.

Relevant code: apps/web/src/components/ChatView.tsx, ChatView.logic.ts, and apps/web/src/j5/squadron/retargetSquadronDraft.ts. Existing policy and store tests passed independently; this extra transition case was non-blocking for the upstream integration's hands-on checkpoint. Avoid introducing a second ownership mechanism or a new balancing policy to make the test easier.