feat(provider): add OpenCode Zen and OpenCode Go providers

Add support for OpenCode Zen (pay-as-you-go, 35+ curated models) and
OpenCode Go ($10/month subscription, open models) as first-class providers.

Both are OpenAI-compatible endpoints resolved via the generic api_key
provider flow — no custom adapter needed.

Files changed:
- hermes_cli/auth.py — ProviderConfig entries + aliases
- hermes_cli/config.py — OPENCODE_ZEN/GO API key env vars
- hermes_cli/models.py — model catalogs, labels, aliases, provider order
- hermes_cli/main.py — provider labels, menu entries, model flow dispatch
- hermes_cli/setup.py — setup wizard branches (idx 10, 11)
- agent/model_metadata.py — context lengths for all OpenCode models
- agent/auxiliary_client.py — default aux models
- .env.example — documentation

Co-authored-by: DevAgarwal2 <DevAgarwal2@users.noreply.github.com>

hermes_cli/auth.py

@@ -163,6 +163,22 @@ PROVIDER_REGISTRY: Dict[str, ProviderConfig] = {
         api_key_env_vars=("AI_GATEWAY_API_KEY",),
         base_url_env_var="AI_GATEWAY_BASE_URL",
     ),
+    "opencode-zen": ProviderConfig(
+        id="opencode-zen",
+        name="OpenCode Zen",
+        auth_type="api_key",
+        inference_base_url="https://opencode.ai/zen/v1",
+        api_key_env_vars=("OPENCODE_ZEN_API_KEY",),
+        base_url_env_var="OPENCODE_ZEN_BASE_URL",
+    ),
+    "opencode-go": ProviderConfig(
+        id="opencode-go",
+        name="OpenCode Go",
+        auth_type="api_key",
+        inference_base_url="https://opencode.ai/zen/go/v1",
+        api_key_env_vars=("OPENCODE_GO_API_KEY",),
+        base_url_env_var="OPENCODE_GO_BASE_URL",
+    ),
 }
 
 
@@ -541,6 +557,8 @@ def resolve_provider(
         "minimax-china": "minimax-cn", "minimax_cn": "minimax-cn",
         "claude": "anthropic", "claude-code": "anthropic",
         "aigateway": "ai-gateway", "vercel": "ai-gateway", "vercel-ai-gateway": "ai-gateway",
+        "opencode": "opencode-zen", "zen": "opencode-zen",
+        "go": "opencode-go", "opencode-go-sub": "opencode-go",
     }
     normalized = _PROVIDER_ALIASES.get(normalized, normalized)