feat(deals): visible unavailable signal for mitigated catalog (closes #42)

When the Deals catalog is empty enrichment now injects
model.options.cmd.unavailable=true while preserving family/cost
and never overwriting Declared cmd. TUI dealsRows returns
banner Deals unavailable — https://commandcode.ai/docs/resources/pricing-limits
with placeholders Tier/Intelligence/Tok/s — instead of hiding,
and cmd_plan_summary keeps No deal data is bundled… path.