feat(provider): add vercel to all gateway-supported fallback entries

Adds vercel to every fallback entry where the model exists on the
gateway (kimi-k2.5, glm-5, glm-4.6v, minimax-m2.7, grok-code-fast-1,
gpt-5-nano). Adds inferSubProvider mappings for minimax, moonshotai,
and zai. Updates librarian/explore special cases to prefer minimax
via gateway over claude-haiku.

src/cli/model-fallback.ts

@@ -129,10 +129,10 @@ export function generateModelConfig(config: InstallConfig): GeneratedOmoConfig {
       let agentConfig: AgentConfig | undefined
       if (avail.opencodeGo) {
         agentConfig = { model: "opencode-go/minimax-m2.7" }
+      } else if (avail.vercelAiGateway) {
+        agentConfig = { model: "vercel/minimax/minimax-m2.7" }
       } else if (avail.zai) {
         agentConfig = { model: ZAI_MODEL }
-      } else if (avail.vercelAiGateway) {
-        agentConfig = { model: "vercel/anthropic/claude-haiku-4.5" }
       }
       if (agentConfig) {
         agents[role] = attachAllFallbackModels(agentConfig, req.fallbackChain, avail)
@@ -149,7 +149,7 @@ export function generateModelConfig(config: InstallConfig): GeneratedOmoConfig {
       } else if (avail.opencodeGo) {
         agentConfig = { model: "opencode-go/minimax-m2.7" }
       } else if (avail.vercelAiGateway) {
-        agentConfig = { model: "vercel/anthropic/claude-haiku-4.5" }
+        agentConfig = { model: "vercel/minimax/minimax-m2.7-highspeed" }
       } else if (avail.copilot) {
         agentConfig = { model: "github-copilot/gpt-5-mini" }
       } else {