feat(compute): 新增 GitHub Copilot 订阅 Provider 预设 (#90)

- compute/providers/github-copilot.json：coding-plan + credentialSource
  github-copilot，models 留空（可用集合随订阅档位与组织策略变化，由客户端
  登录后经 /models 动态发现）
- schemas/provider.schema.json：credentialSource 枚举登记 github-copilot 及其语义
- _index.json 顺序追加；manifest presetDataVersion 105 → 106
- 测试计价归属表登记 github-copilot（USD）

Co-authored-by: yi-ge <jackyoncode@gmail.com>

compute/providers/_index.json

@@ -5,6 +5,7 @@
     "openai-codex",
     "anthropic",
     "anthropic-claude",
+    "github-copilot",
     "deepseek",
     "dashscope",
     "volcengine",

compute/providers/github-copilot.json

@@ -0,0 +1,28 @@
+{
+  "id": "provider-github-copilot-plan-001",
+  "provider": "github-copilot",
+  "brandGroup": "github",
+  "label": "GitHub Copilot 订阅",
+  "baseUrl": "https://api.githubcopilot.com",
+  "apiFormat": "openai-completions",
+  "apiKeyRef": "github-copilot-session-token",
+  "apiKeyVerified": false,
+  "enabled": false,
+  "status": "unconfigured",
+  "priceCurrency": "USD",
+  "accessMode": "coding-plan",
+  "credentialSource": "github-copilot",
+  "requiredClientVersion": "10.0.132",
+  "codingPlan": {
+    "quotas": {},
+    "usageTracking": {
+      "method": "none",
+      "consoleUrl": "https://github.com/settings/copilot/features"
+    }
+  },
+  "services": [
+    "chat",
+    "reasoning"
+  ],
+  "models": []
+}