fix: preserve dots in model names for OpenCode Zen and ZAI providers (#8794)

OpenCode Zen was in _DOT_TO_HYPHEN_PROVIDERS, causing all dotted model
names (minimax-m2.5-free, gpt-5.4, glm-5.1) to be mangled. The fix:

Layer 1 (model_normalize.py): Remove opencode-zen from the blanket
dot-to-hyphen set. Add an explicit block that preserves dots for
non-Claude models while keeping Claude hyphenated (Zen's Claude
endpoint uses anthropic_messages mode which expects hyphens).

Layer 2 (run_agent.py _anthropic_preserve_dots): Add opencode-zen and
zai to the provider allowlist. Broaden URL check from opencode.ai/zen/go
to opencode.ai/zen/ to cover both Go and Zen endpoints. Add bigmodel.cn
for ZAI URL detection.

Also adds glm-5.1 to ZAI model lists in models.py and setup.py.

Closes #7710

Salvaged from contributions by:
- konsisumer (PR #7739, #7719)
- DomGrieco (PR #8708)
- Esashiero (PR #7296)
- sharziki (PR #7497)
- XiaoYingGee (PR #8750)
- APTX4869-maker (PR #8752)
- kagura-agent (PR #7157)

run_agent.py

@@ -5856,11 +5856,12 @@ class AIAgent:
         """True when using an anthropic-compatible endpoint that preserves dots in model names.
         Alibaba/DashScope keeps dots (e.g. qwen3.5-plus).
         MiniMax keeps dots (e.g. MiniMax-M2.7).
-        OpenCode Go keeps dots (e.g. minimax-m2.7)."""
-        if (getattr(self, "provider", "") or "").lower() in {"alibaba", "minimax", "minimax-cn", "opencode-go"}:
+        OpenCode Go/Zen keeps dots for non-Claude models (e.g. minimax-m2.5-free).
+        ZAI/Zhipu keeps dots (e.g. glm-4.7, glm-5.1)."""
+        if (getattr(self, "provider", "") or "").lower() in {"alibaba", "minimax", "minimax-cn", "opencode-go", "opencode-zen", "zai"}:
             return True
         base = (getattr(self, "base_url", "") or "").lower()
-        return "dashscope" in base or "aliyuncs" in base or "minimax" in base or "opencode.ai/zen/go" in base
+        return "dashscope" in base or "aliyuncs" in base or "minimax" in base or "opencode.ai/zen/" in base or "bigmodel.cn" in base
 
     def _is_qwen_portal(self) -> bool:
         """Return True when the base URL targets Qwen Portal."""