[FEATURE] User control over prompt suggestions under usage limits (keep available at allowed_warning, optional lighter model)

What

Give users explicit control over inline prompt suggestions when the account is
near its weekly usage limit, instead of silently suppressing them in the
allowed_warning state (see bug #72495).

Why

When near the weekly limit the session is still fully usable, but the ambient
ghost-text "next step" hint disappears — which is exactly when, mid long agentic
or multi-step work, it's most useful for keeping momentum. Several reports show
strong, and notably bidirectional, demand for control over this feature:

• Want it kept on / restored: #30699 (multiple users, incl. recent), #36733

(per-turn toggle, cost-aware).

• Want it off: #71788, #66117 (find it distracting / intrusive).

The common thread is that users want to control suggestions — both directions —
rather than have them silently appear or vanish based on hidden state.

Proposal (any one would help)

1. Treat allowed_warning as usable for suggestions — the bug fix in

#72495; suppress only on actual exhaustion.

1. A /config toggle + ~/.claude/settings.json setting for suggestions

(on / off / keep-on-under-limit), accepting the usage tradeoff when on.

1. Optionally generate suggestions with a lighter model (e.g. Sonnet or

Haiku) under constrained usage, so the cost of keeping them on near the limit
is negligible.

Related

#72495 (the suppression bug), #57822 (same strict-equality class, fixed),
#30699 (restore requests), #36733 (toggle request), #71788 / #66117 (off-switch
requests).