feat: add Venice AI provider integration

Venice AI is a privacy-focused AI inference provider with support for
uncensored models and access to major proprietary models via their
anonymized proxy.

This integration adds:

- Complete model catalog with 25 models:
  - 15 private models (Llama, Qwen, DeepSeek, Venice Uncensored, etc.)
  - 10 anonymized models (Claude, GPT-5.2, Gemini, Grok, Kimi, MiniMax)
- Auto-discovery from Venice API with fallback to static catalog
- VENICE_API_KEY environment variable support
- Interactive onboarding via 'venice-api-key' auth choice
- Model selection prompt showing all available Venice models
- Provider auto-registration when API key is detected
- Comprehensive documentation covering:
  - Privacy modes (private vs anonymized)
  - All 25 models with context windows and features
  - Streaming, function calling, and vision support
  - Model selection recommendations

Privacy modes:
- Private: Fully private, no logging (open-source models)
- Anonymized: Proxied through Venice (proprietary models)

Default model: venice/llama-3.3-70b (good balance of capability + privacy)
Venice API: https://api.venice.ai/api/v1 (OpenAI-compatible)

src/commands/onboard-auth.credentials.ts

@@ -99,6 +99,19 @@ export async function setSyntheticApiKey(key: string, agentDir?: string) {
   });
 }
 
+export async function setVeniceApiKey(key: string, agentDir?: string) {
+  // Write to resolved agent dir so gateway finds credentials on startup.
+  upsertAuthProfile({
+    profileId: "venice:default",
+    credential: {
+      type: "api_key",
+      provider: "venice",
+      key,
+    },
+    agentDir: resolveAuthAgentDir(agentDir),
+  });
+}
+
 export const ZAI_DEFAULT_MODEL_REF = "zai/glm-4.7";
 export const OPENROUTER_DEFAULT_MODEL_REF = "openrouter/auto";
 export const VERCEL_AI_GATEWAY_DEFAULT_MODEL_REF = "vercel-ai-gateway/anthropic/claude-opus-4.5";