feat(app): Align desktop model picker visibility with TUI

[jc-244]

What does this PR do?

This PR aligns Desktop behavior with TUI:

• Default visibility: show all non-deprecated models based on the provider.
  Fixes: [FEATURE]: Expand model picker options after OAuth subscription #10560

How did you verify your code works?

Comparing desktop model list with that of TUI

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[adamdotdevin]

I'm not following, can you elaborate?

[jc-244]

I'm not following, can you elaborate?

The intent here is simply: expose more model choices in the Desktop model picker (to match what TUI already exposes).

Motivation:
I sometimes need an older/smaller variant (e.g. GPT‑5.1‑mini), and it was being hidden by the family-based dedupe.

What TUI does:

• TUI does not dedupe by family at all. It basically lists all models for a provider and only filters out deprecated ones:

opencode/packages/opencode/src/cli/cmd/tui/component/dialog-model.tsx

Lines 121 to 126 in b24fd90

	pipe(
	provider.models,
	entries(),
	filter(([_, info]) => info.status !== "deprecated"),
	filter(([_, info]) => (props.providerID ? info.providerID === props.providerID : true)),
	map(([model, info]) => {

• There is already a allowlist for openai codex model provider

opencode/packages/opencode/src/plugin/codex.ts

Lines 358 to 364 in b24fd90

	const allowedModels = new Set([
	"gpt-5.1-codex-max",
	"gpt-5.1-codex-mini",
	"gpt-5.2",
	"gpt-5.2-codex",
	"gpt-5.1-codex",
	])

What Desktop was doing:

• Desktop had an extra gating by family values, so only one model per family showed up by default, which is why those additional variants weren’t visible.

What this change does:

• Stop using family to collapse/dedupe the default-visible set, so more provider models become selectable in Desktop (while still keeping deprecated hidden; and if we want, we can still keep the existing “recent window” constraint to avoid showing truly old models). @adamdotdevin