feat(agent): unify models and validate OpenCode providers

Generate chat, task and learning models from agent-models.json.
Use WaterNetwork fast/expert models with 272k context and validate
upstream names before readiness. Add an isolated model check command
with signal-safe cleanup and plugin, Skill and MCP management docs.

Verified in isolation: type checks, 26 focused tests and both model
catalog checks; no model inference requests.

.opencode/tjwater-plugin/package.json

@@ -1,6 +1,7 @@
 {
   "name": "tjwater-tools-plugin",
   "version": "1.0.0",
+  "description": "TJWater 供水 Agent 的 OpenCode 插件：业务工具、Skill 管理、MCP 会话策略、Shell 沙箱与模型校验。",
   "private": true,
   "type": "module",
   "exports": "./index.ts"