feat(zai): add Z.AI GLM Coding Plan provider preset (#896)

* feat(zai): add Z.AI GLM Coding Plan provider preset

Add dedicated Z.AI provider support for the GLM Coding Plan, enabling
use of GLM-5.1, GLM-5-Turbo, GLM-4.7, and GLM-4.5-Air models through
the OpenAI-compatible shim with proper thinking mode (reasoning_content),
max_tokens handling, and context window sizing.

* fix(zai): unify GLM max output token limits across casing variants

glm-5/glm-4.7 had conservative 16K max output while GLM-5/GLM-4.7
had 131K. Use consistent Z.AI coding plan limits for all GLM variants.

* fix(zai): restore DashScope GLM limits, enable GLM thinking support

- Restore lowercase glm-5/glm-4.7 to 16_384 max output (DashScope limits)
  while keeping Z.AI coding plan high limits on uppercase GLM-* keys only
- Add GLM model support to modelSupportsThinking() so reasoning_content
  is enabled when using GLM-5.x/GLM-4.7 models on Z.AI

* fix(zai): tighten GLM regexes, fix misleading context window comment

- Use precise regex in thinking.ts: exact GLM model matches only,
  no false positives on glm-50/glm-4, includes glm-4.5-air
- Use uppercase-only match in StartupScreen rawModel fallback so
  DashScope lowercase glm-* models aren't mislabeled as Z.AI
- Clarify context window comment: lowercase glm-5.1/glm-5-turbo/
  glm-4.5-air are Z.AI-specific aliases, not DashScope

* fix(zai): scope GLM detection to Z.AI

* improve readability of max_completion_tokens check

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

src/utils/providerDiscovery.ts

@@ -1,5 +1,6 @@
 import type { OllamaModelDescriptor } from './providerRecommendation.ts'
 import { DEFAULT_OPENAI_BASE_URL } from '../services/api/providerConfig.js'
+import { isZaiBaseUrl } from './zaiProvider.js'
 
 export const DEFAULT_OLLAMA_BASE_URL = 'http://localhost:11434'
 export const DEFAULT_ATOMIC_CHAT_BASE_URL = 'http://127.0.0.1:1337'
@@ -205,6 +206,10 @@ export function getLocalOpenAICompatibleProviderLabel(baseUrl?: string): string
     if (host.includes('bankr') || haystack.includes('bankr')) {
       return 'Bankr'
     }
+    // Z.AI GLM Coding Plan
+    if (isZaiBaseUrl(parsed.href)) {
+      return 'Z.AI - GLM'
+    }
     // Moonshot AI direct API
     if (
       host.includes('moonshot') ||