Feat/litellm provider (#12823)

* feat: add LiteLLM provider types, env var, credentials, and auth choice

Add litellm-api-key auth choice, LITELLM_API_KEY env var mapping,
setLitellmApiKey() credential storage, and LITELLM_DEFAULT_MODEL_REF.

* feat: add LiteLLM onboarding handler and provider config

Add applyLitellmProviderConfig which properly registers
models.providers.litellm with baseUrl, api type, and model definitions.
This fixes the critical bug from PR #6488 where the provider entry was
never created, causing model resolution to fail at runtime.

* docs: add LiteLLM provider documentation

Add setup guide covering onboarding, manual config, virtual keys,
model routing, and usage tracking. Link from provider index.

* docs: add LiteLLM to sidebar navigation in docs.json

Add providers/litellm to both English and Chinese provider page lists
so the docs page appears in the sidebar navigation.

* test: add LiteLLM non-interactive onboarding test

Wire up litellmApiKey flag inference and auth-choice handler for the
non-interactive onboarding path, and add an integration test covering
profile, model default, and credential storage.

* fix: register --litellm-api-key CLI flag and add preferred provider mapping

Wire up the missing Commander CLI option, action handler mapping, and
help text for --litellm-api-key. Add litellm-api-key to the preferred
provider map for consistency with other providers.

* fix: remove zh-CN sidebar entry for litellm (no localized page yet)

* style: format buildLitellmModelDefinition return type

* fix(onboarding): harden LiteLLM provider setup (#12823)

* refactor(onboarding): keep auth-choice provider dispatcher under size limit

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/commands/onboard-non-interactive/local/auth-choice-inference.ts

@@ -23,6 +23,7 @@ type AuthChoiceFlagOptions = Pick<
   | "minimaxApiKey"
   | "opencodeZenApiKey"
   | "xaiApiKey"
+  | "litellmApiKey"
 >;
 
 const AUTH_CHOICE_FLAG_MAP = [
@@ -45,6 +46,7 @@ const AUTH_CHOICE_FLAG_MAP = [
   { flag: "xaiApiKey", authChoice: "xai-api-key", label: "--xai-api-key" },
   { flag: "minimaxApiKey", authChoice: "minimax-api", label: "--minimax-api-key" },
   { flag: "opencodeZenApiKey", authChoice: "opencode-zen", label: "--opencode-zen-api-key" },
+  { flag: "litellmApiKey", authChoice: "litellm-api-key", label: "--litellm-api-key" },
 ] satisfies ReadonlyArray<AuthChoiceFlag>;
 
 export type AuthChoiceInference = {

src/commands/onboard-non-interactive/local/auth-choice.ts

@@ -24,6 +24,7 @@ import {
   applyVeniceConfig,
   applyTogetherConfig,
   applyVercelAiGatewayConfig,
+  applyLitellmConfig,
   applyXaiConfig,
   applyXiaomiConfig,
   applyZaiConfig,
@@ -32,6 +33,7 @@ import {
   setQianfanApiKey,
   setGeminiApiKey,
   setKimiCodingApiKey,
+  setLitellmApiKey,
   setMinimaxApiKey,
   setMoonshotApiKey,
   setOpencodeZenApiKey,
@@ -314,6 +316,29 @@ export async function applyNonInteractiveAuthChoice(params: {
     return applyOpenrouterConfig(nextConfig);
   }
 
+  if (authChoice === "litellm-api-key") {
+    const resolved = await resolveNonInteractiveApiKey({
+      provider: "litellm",
+      cfg: baseConfig,
+      flagValue: opts.litellmApiKey,
+      flagName: "--litellm-api-key",
+      envVar: "LITELLM_API_KEY",
+      runtime,
+    });
+    if (!resolved) {
+      return null;
+    }
+    if (resolved.source !== "profile") {
+      await setLitellmApiKey(resolved.key);
+    }
+    nextConfig = applyAuthProfileConfig(nextConfig, {
+      profileId: "litellm:default",
+      provider: "litellm",
+      mode: "api_key",
+    });
+    return applyLitellmConfig(nextConfig);
+  }
+
   if (authChoice === "ai-gateway-api-key") {
     const resolved = await resolveNonInteractiveApiKey({
       provider: "vercel-ai-gateway",