feat(providers): expose gpt-4o on built-in GitHub Copilot (gh) provider

[diegosouzapw]

Summary

Adds the original gpt-4o chat model to OmniRoute's built-in GitHub Copilot provider (github / alias gh).

GitHub Copilot's /chat/completions endpoint still serves gpt-4o, but OmniRoute's registry only listed the GPT-5.x family under gh, so apps that hard-code gpt-4o against this provider resolved to "unknown model". The entry is added next to the GPT-5.x lineup with contextLength: 128000 and no openai-responses targetFormat, so it routes via the provider default (/chat/completions) — the same lane the Claude/Gemini Copilot entries use after #2911.

Why this change

• Parity with the upstream GitHub Copilot catalog (still serves GPT-4o).
• Restores the model for clients that pin gh/gpt-4o (Cursor IDE, scripts, evals).
• No effect on GPT-5.x / Claude / Gemini / Raptor entries already curated here.

Changes

• open-sse/config/providers/registry/github/index.ts — add { id: "gpt-4o", name: "GPT-4o", contextLength: 128000 } at the top of models[] (chat/completions lane, no openai-responses).
• tests/unit/provider-registry-github-copilot-gpt-4o.test.ts — new TDD test (RED before the edit, GREEN after):
  • gpt-4o is registered under the github provider
  • It does not carry openai-responses targetFormat (would 400 — Copilot Responses API does not serve it)
  • It is reachable via getModelsByProviderId("github")
• CHANGELOG.md — [3.8.32] → ### ✨ New Features entry, credited to upstream author.

Validation

• node --import tsx/esm --test tests/unit/provider-registry-github-copilot-gpt-4o.test.ts tests/unit/provider-registry-github-copilot-targetformat.test.ts → 11 pass / 0 fail (3 new + 8 sibling [BUG] Built-in GitHub Copilot listed Claude Opus/Gemini models fail due to API format/routing #2911 regressions).
• npm run typecheck:core → clean.
• npx eslint on touched files → clean.

Ported from

decolua/9router#98 — single-line addition to providerModels.js. Original author credited via Co-authored-by: trailer (Bexultan).

Test plan

• TDD test added and passes
• Sibling Copilot test ([BUG] Built-in GitHub Copilot listed Claude Opus/Gemini models fail due to API format/routing #2911) still passes
• Typecheck clean
• Lint clean on touched files

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[gemini-code-assist]

Code Review

This pull request adds the gpt-4o model to the GitHub Copilot provider registry and introduces unit tests to verify its registration and routing configuration. The reviewer suggests using static import statements instead of top-level dynamic imports in the test file to improve static analysis and maintain idiomatic TypeScript.

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[gemini-code-assist]

Using static import statements is preferred over top-level dynamic await import(...) unless there is a specific reason for lazy loading or conditional importing. Static imports allow for better static analysis, type checking, and are more idiomatic in TypeScript.

Suggested change

	const { REGISTRY } = await import("../../open-sse/config/providerRegistry.ts");
	const { getModelsByProviderId } = await import("../../open-sse/config/providerModels.ts");
	import { REGISTRY } from "../../open-sse/config/providerRegistry.ts";
	import { getModelsByProviderId } from "../../open-sse/config/providerModels.ts";