feat(agents): simplify GPT detection to name-based check, add hephaestus providers (venice uses gpt-5.3-codex)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/agents/types.test.ts

@@ -2,11 +2,17 @@ import { describe, test, expect } from "bun:test";
 import { isGptModel, isGeminiModel } from "./types";
 
 describe("isGptModel", () => {
-  test("standard openai provider models", () => {
+  test("standard openai provider gpt models", () => {
     expect(isGptModel("openai/gpt-5.2")).toBe(true);
     expect(isGptModel("openai/gpt-4o")).toBe(true);
-    expect(isGptModel("openai/o1")).toBe(true);
-    expect(isGptModel("openai/o3-mini")).toBe(true);
+  });
+
+  test("o-series models are not gpt by name", () => {
+    expect(isGptModel("openai/o1")).toBe(false);
+    expect(isGptModel("openai/o3-mini")).toBe(false);
+    expect(isGptModel("litellm/o1")).toBe(false);
+    expect(isGptModel("litellm/o3-mini")).toBe(false);
+    expect(isGptModel("litellm/o4-mini")).toBe(false);
   });
 
   test("github copilot gpt models", () => {
@@ -17,9 +23,6 @@ describe("isGptModel", () => {
   test("litellm proxied gpt models", () => {
     expect(isGptModel("litellm/gpt-5.2")).toBe(true);
     expect(isGptModel("litellm/gpt-4o")).toBe(true);
-    expect(isGptModel("litellm/o1")).toBe(true);
-    expect(isGptModel("litellm/o3-mini")).toBe(true);
-    expect(isGptModel("litellm/o4-mini")).toBe(true);
   });
 
   test("other proxied gpt models", () => {
@@ -27,6 +30,11 @@ describe("isGptModel", () => {
     expect(isGptModel("custom-provider/gpt-5.2")).toBe(true);
   });
 
+  test("venice provider gpt models", () => {
+    expect(isGptModel("venice/gpt-5.2")).toBe(true);
+    expect(isGptModel("venice/gpt-4o")).toBe(true);
+  });
+
   test("gpt4 prefix without hyphen (legacy naming)", () => {
     expect(isGptModel("litellm/gpt4o")).toBe(true);
     expect(isGptModel("ollama/gpt4")).toBe(true);