[FEATURE]: Omen Alpha — free trial window or separate quota bucket (the Ox Alpha precedent)

✅ Verified — no existing issue covers this (searched omen-alpha before opening).

The request: give the current stealth model Omen Alpha one of the two access patterns OpenCode has already proven with earlier stealth launches:

1. A time-boxed free window with generous rate limits — exactly how Ox Alpha launched ("free for the next week, generous rate limits"), which produced record usage, a wave of community feedback, and a clean reveal as GLM-5.3-Flash; or
2. A separate Omen Alpha quota bucket, so trying it doesn't drain the main Go subscription.

Why this matters: right now Omen Alpha is paid-only and billed against the shared subscription quota. During a stealth window — the single most valuable feedback period for the team — many users self-limit to a handful of prompts (or skip it entirely) because every trial message eats into the budget they need for daily work. That shrinks and skews the feedback collected before the reveal. Ox Alpha's free window worked precisely because it removed that trade-off.

Big Pickle, MiMo-V2.5 Free and the Nemotron free windows show this is already the house style for stealth/community models — Omen Alpha is the first stealth launch where the model itself sits behind the paywall.

Happy to contribute structured eval notes in exchange (I run it daily through a coding-agent harness with the full 500K context: multi-step tasks, tool-calling reliability, failure modes).

The issue names no files, tests, or entry points. Start by locating the existing Omen Alpha access and quota handling, then compare the Ox Alpha, Big Pickle, MiMo-V2.5 Free, and Nemotron launch paths; done means either a free trial window or a separate quota bucket lets users try Omen Alpha without consuming the shared Go subscription quota.