config: variants documented as array but schema requires object — provider silently dropped #53744

Summary

The models doc shows model variants as an array of { id, settings }
objects, but the published config schema requires variants to be an
object keyed by variant ID. Config following the documented array form
fails schema validation, and the failure is silent: the entire provider
is dropped from the model list with no error or warning at config load.

Environment

• opencode version: v2.0.24
• OS: Darwin 25.6.0 (arm64, Apple M-series)
• Terminal: Ghostty (TERM_PROGRAM=ghostty, COLORTERM=truecolor)
• Shell: /bin/zsh
• Install/channel: latest
• Active plugins: superpowers (project config, bare npm name), superpowers@git+https://github.com/obra/superpowers.git (global config)

Reproduction

1. Configure a custom OpenAI-compatible provider, copying the documented
   variants array form from the models guide (https://opencode.ai/v2/docs/models, "Variants" section):

   {
     "$schema": "https://opencode.ai/config.json",
     "model": "local/some-model",
     "providers": {
       "local": {
         "package": "@opencode/ai/providers/openai-compatible",
         "settings": { "baseURL": "http://127.0.0.1:8000/v1" },
         "models": {
           "some-model": {
             "limit": { "context": 1000, "output": 1000 },
             // Exactly as documented in the "Variants" section:
             "variants": [
               { "id": "low", "settings": { "reasoningEffort": "low" } },
               { "id": "high", "settings": { "reasoningEffort": "high" } }
             ]
           }
         }
       }
     }
   }

2. Start OpenCode (or open /models in the TUI).

Expected Behavior

The provider's model appears in the model selector with #low / #high
variants selectable, matching the documented example.

Actual Behavior

• No error or warning is reported for the config.
• The provider's model is absent from the model selector; the provider
  appears to have been dropped entirely.
• Starting a session on that model fails with:
  Unsupported package for local/some-model:

Replacing the array with the object form resolves it immediately:

"variants": {
  "low":  { "settings": { "reasoningEffort": "low" } },
  "high": { "settings": { "reasoningEffort": "high" } }
}

Additional Context

• The published schema (https://opencode.ai/config.json) defines the model
  variants field as {"type": "object", "additionalProperties": {...}} —
  i.e. a map of variant ID → config — while the models guide shows an array.
  The two official sources contradict each other; one of them needs fixing.
• The more dangerous part is the silent failure mode: an invalid variants
  shape drops the whole provider with no diagnostic, so the user sees only
  "model missing" / "unsupported package" and has no hint to look at the
  config. A config-validation error (or a warning naming the offending field)
  would make this tractable.
• Consistently reproducible (not intermittent).