feat: upgrade MiniMax from M2.5 to M2.7 and expand to more agents/categories

- Upgrade minimax-m2.5 → minimax-m2.7 (latest model) across all agents and categories
- Replace minimax-m2.5-free with minimax-m2.7-highspeed (optimized speed variant)
- Expand MiniMax fallback coverage to atlas, sisyphus-junior, writing, and unspecified-low
- Add isMiniMaxModel() detection function in types.ts for model family detection
- Update all tests (58 passing) and documentation

src/agents/AGENTS.md

@@ -13,8 +13,8 @@ Agent factories following `createXXXAgent(model) → AgentConfig` pattern. Each
 | **Sisyphus** | claude-opus-4-6 max | 0.1 | all | k2p5 → kimi-k2.5 → gpt-5.4 medium → glm-5 → big-pickle | Main orchestrator, plans + delegates |
 | **Hephaestus** | gpt-5.3-codex medium | 0.1 | all | gpt-5.4 medium (copilot) | Autonomous deep worker |
 | **Oracle** | gpt-5.4 high | 0.1 | subagent | gemini-3.1-pro high → claude-opus-4-6 max | Read-only consultation |
-| **Librarian** | gemini-3-flash | 0.1 | subagent | minimax-m2.5-free → big-pickle | External docs/code search |
-| **Explore** | grok-code-fast-1 | 0.1 | subagent | minimax-m2.5-free → claude-haiku-4-5 → gpt-5-nano | Contextual grep |
+| **Librarian** | minimax-m2.7 | 0.1 | subagent | minimax-m2.7-highspeed → claude-haiku-4-5 → gpt-5-nano | External docs/code search |
+| **Explore** | grok-code-fast-1 | 0.1 | subagent | minimax-m2.7-highspeed → minimax-m2.7 → claude-haiku-4-5 → gpt-5-nano | Contextual grep |
 | **Multimodal-Looker** | gpt-5.3-codex medium | 0.1 | subagent | k2p5 → gemini-3-flash → glm-4.6v → gpt-5-nano | PDF/image analysis |
 | **Metis** | claude-opus-4-6 max | **0.3** | subagent | gpt-5.4 high → gemini-3.1-pro high | Pre-planning consultant |
 | **Momus** | gpt-5.4 xhigh | 0.1 | subagent | claude-opus-4-6 max → gemini-3.1-pro high | Plan reviewer |

src/agents/types.test.ts

@@ -1,5 +1,5 @@
 import { describe, test, expect } from "bun:test";
-import { isGptModel, isGeminiModel, isGpt5_4Model } from "./types";
+import { isGptModel, isGeminiModel, isGpt5_4Model, isMiniMaxModel } from "./types";
 
 describe("isGpt5_4Model", () => {
   test("detects gpt-5.4 models", () => {
@@ -79,6 +79,28 @@ describe("isGptModel", () => {
   });
 });
 
+describe("isMiniMaxModel", () => {
+  test("detects minimax models with provider prefix", () => {
+    expect(isMiniMaxModel("opencode-go/minimax-m2.7")).toBe(true);
+    expect(isMiniMaxModel("opencode/minimax-m2.7-highspeed")).toBe(true);
+    expect(isMiniMaxModel("opencode-go/minimax-m2.5")).toBe(true);
+    expect(isMiniMaxModel("opencode/minimax-m2.5-free")).toBe(true);
+  });
+
+  test("detects minimax models without provider prefix", () => {
+    expect(isMiniMaxModel("minimax-m2.7")).toBe(true);
+    expect(isMiniMaxModel("minimax-m2.7-highspeed")).toBe(true);
+    expect(isMiniMaxModel("minimax-m2.5")).toBe(true);
+  });
+
+  test("does not match non-minimax models", () => {
+    expect(isMiniMaxModel("openai/gpt-5.4")).toBe(false);
+    expect(isMiniMaxModel("anthropic/claude-opus-4-6")).toBe(false);
+    expect(isMiniMaxModel("google/gemini-3.1-pro")).toBe(false);
+    expect(isMiniMaxModel("opencode-go/kimi-k2.5")).toBe(false);
+  });
+});
+
 describe("isGeminiModel", () => {
   test("#given google provider models #then returns true", () => {
     expect(isGeminiModel("google/gemini-3.1-pro")).toBe(true);

src/agents/types.ts

@@ -91,6 +91,11 @@ export function isGpt5_3CodexModel(model: string): boolean {
 
 const GEMINI_PROVIDERS = ["google/", "google-vertex/"];
 
+export function isMiniMaxModel(model: string): boolean {
+  const modelName = extractModelName(model).toLowerCase();
+  return modelName.includes("minimax");
+}
+
 export function isGeminiModel(model: string): boolean {
   if (GEMINI_PROVIDERS.some((prefix) => model.startsWith(prefix))) return true;