feat(providers): declare reasoning efforts so xhigh/max surface in the UI

The settings effort dropdown is driven by a model's reasoning.efforts and
falls back to [low, medium, high] when absent, so xhigh/max were never
selectable for OpenAI-compatible models even though the backend accepts them.

Declare the verified accepted levels:
- glm-5.2: [high, max] (Z.AI: GLM-5.2 reasoning_effort accepts only high/max,
  so the default low/medium were also wrong for it)
- gpt-5.4: [low, medium, high, xhigh] (OpenAI GPT-5.4/5.5 effort enum)

Other openai/gpt-5.x entries still need per-model effort verification.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/pkg/providers/glm/models.yml

@@ -2,6 +2,8 @@
 - name: glm-5.2
   description: GLM-5.2 - Newest flagship (improves on GLM-5.1), 200K context, hybrid thinking; supports reasoning_effort (high/max).
   thinking: true
+  reasoning:
+    efforts: [high, max]
   price:
     input: 1.40
     output: 4.40

backend/pkg/providers/openai/models.yml

@@ -2,6 +2,8 @@
 - name: gpt-5.4
   description: Best intelligence at scale for agentic, coding, and professional workflows. Flagship model with 1M context window and configurable reasoning effort (none/low/medium/high/xhigh). Excels at complex professional work, sophisticated security research, and advanced autonomous penetration testing requiring maximum cognitive depth and accuracy.
   thinking: true
+  reasoning:
+    efforts: [low, medium, high, xhigh]
   release_date: 2026-01-15
   price:
     input: 2.5