feat: multi-provider support — Ollama Cloud + OpenCode Go

- Account.Provider field (ollama-cloud | opencode-go), backward compatible
- Model-based routing: common models served by combined pool, unique models
  routed to their provider only
- /go/v1/* path forces OpenCode Go provider (prefix stripped upstream)
- Merged /v1/models endpoint returns union of both catalogs (44 models)
- Failover: 429/402 → cooldown + failover; 5xx → retry without cooldown
- CLI: accounts add --provider flag, list shows provider column
- Body buffering: request body buffered (8 MiB cap) for failover replay
- opencode integration: unified provider 'oc' with all merged models
- 64 tests pass (unit + integration)
- Verified: glm-5 → ollama, mimo-v2.5 → go, gpt-oss:20b → ollama

internal/cli/accounts.go

@@ -37,16 +37,21 @@ func RunAccounts(args []string) int {
 
 func printAccountsUsage() {
 	fmt.Print(`Usage:
-  ollama-proxy accounts add [API_KEY] [--name <alias>]
+  ollama-proxy accounts add [API_KEY] [--name <alias>] [--provider ollama-cloud|opencode-go]
   ollama-proxy accounts list
   ollama-proxy accounts remove <id|name>
   ollama-proxy accounts set-base-url <url>
+
+Providers:
+  ollama-cloud   (default) Ollama Cloud at https://ollama.com — native + OpenAI API
+  opencode-go    OpenCode Go at https://opencode.ai/zen/go/v1 — OpenAI API only
 `)
 }
 
-// accountsAdd implements `accounts add [API_KEY] [--name <alias>]`.
+// accountsAdd implements `accounts add [API_KEY] [--name <alias>] [--provider P]`.
 func accountsAdd(args []string) int {
 	var apiKey, name string
+	provider := config.ProviderOllamaCloud
 	for i := 0; i < len(args); i++ {
 		switch args[i] {
 		case "--name":
@@ -56,8 +61,15 @@ func accountsAdd(args []string) int {
 			}
 			name = args[i+1]
 			i++
+		case "--provider":
+			if i+1 >= len(args) {
+				fmt.Fprintln(os.Stderr, "--provider requires an argument")
+				return 2
+			}
+			provider = config.ProviderType(args[i+1])
+			i++
 		case "-h", "--help":
-			fmt.Println("usage: accounts add [API_KEY] [--name <alias>]")
+			fmt.Println("usage: accounts add [API_KEY] [--name <alias>] [--provider ollama-cloud|opencode-go]")
 			return 0
 		default:
 			if apiKey == "" {
@@ -69,6 +81,11 @@ func accountsAdd(args []string) int {
 		}
 	}
 
+	if !config.ValidProvider(provider) {
+		fmt.Fprintf(os.Stderr, "unknown provider %q (use ollama-cloud or opencode-go)\n", provider)
+		return 2
+	}
+
 	if name == "" {
 		name = promptString("Account name (alias)", "acct"+config.NewID()[:4])
 	}
@@ -78,7 +95,14 @@ func accountsAdd(args []string) int {
 	}
 
 	if apiKey == "" {
-		fmt.Print("Enter Ollama Cloud API key (input hidden): ")
+		label := "API key"
+		switch provider {
+		case config.ProviderOpenCodeGo:
+			label = "OpenCode Go API key"
+		case config.ProviderOllamaCloud:
+			label = "Ollama Cloud API key"
+		}
+		fmt.Printf("Enter %s (input hidden): ", label)
 		b, err := term.ReadPassword(int(os.Stdin.Fd()))
 		fmt.Println()
 		if err != nil {
@@ -106,17 +130,19 @@ func accountsAdd(args []string) int {
 		return 2
 	}
 	acct := config.Account{
-		ID:      config.NewID(),
-		Name:    name,
-		APIKey:  apiKey,
-		Created: nowFn(),
+		ID:       config.NewID(),
+		Name:     name,
+		Provider: provider,
+		APIKey:   apiKey,
+		Created:  nowFn(),
 	}
 	af.Accounts = append(af.Accounts, acct)
 	if err := af.Save(); err != nil {
 		fmt.Fprintln(os.Stderr, "save accounts:", err)
 		return 1
 	}
-	fmt.Printf("added account %s (name=%s key=%s)\n", acct.ID[:8], acct.Name, maskKey(acct.APIKey))
+	fmt.Printf("added account %s (name=%s provider=%s key=%s)\n",
+		acct.ID[:8], acct.Name, acct.Provider, maskKey(acct.APIKey))
 	return 0
 }
 
@@ -133,15 +159,21 @@ func accountsList(args []string) int {
 	}
 	w := bufio.NewWriter(os.Stdout)
 	defer w.Flush()
-	fmt.Fprintf(w, "%-10s %-16s %-18s %-22s\n", "ID", "NAME", "KEY", "CREATED")
-	fmt.Fprintf(w, "%-10s %-16s %-18s %-22s\n", strings.Repeat("-", 8), strings.Repeat("-", 14), strings.Repeat("-", 16), strings.Repeat("-", 20))
+	fmt.Fprintf(w, "%-10s %-14s %-16s %-18s %-22s\n", "ID", "PROVIDER", "NAME", "KEY", "CREATED")
+	fmt.Fprintf(w, "%-10s %-14s %-16s %-18s %-22s\n",
+		strings.Repeat("-", 8), strings.Repeat("-", 12), strings.Repeat("-", 14),
+		strings.Repeat("-", 16), strings.Repeat("-", 20))
 	for _, a := range af.Accounts {
 		id := a.ID
 		if len(id) > 8 {
 			id = id[:8]
 		}
+		prov := string(a.Provider)
+		if prov == "" {
+			prov = string(config.ProviderOllamaCloud)
+		}
 		created := a.Created.Format("2006-01-02 15:04 MST")
-		fmt.Fprintf(w, "%-10s %-16s %-18s %-22s\n", id, a.Name, maskKey(a.APIKey), created)
+		fmt.Fprintf(w, "%-10s %-14s %-16s %-18s %-22s\n", id, prov, a.Name, maskKey(a.APIKey), created)
 	}
 	if af.BaseURL != "" {
 		fmt.Fprintf(w, "\nDefault upstream: %s\n", af.BaseURL)