refactor(v2): move opencode provider off v2 trunk

v2 ships with only claude baked in. opencode now lives on the `providers`
branch and gets copied in via the /add-opencode skill.

Removed:
- src/providers/opencode.ts
- container/agent-runner/src/providers/{opencode,mcp-to-opencode}.ts + test
- @opencode-ai/sdk from agent-runner package.json + bun.lock
- opencode-ai global install + OPENCODE_VERSION ARG from Dockerfile
- opencode self-registration imports from both provider barrels
- opencode test case from factory.test.ts

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

container/agent-runner/bun.lock

@@ -7,7 +7,6 @@
       "dependencies": {
         "@anthropic-ai/claude-agent-sdk": "^0.2.92",
         "@modelcontextprotocol/sdk": "^1.12.1",
-        "@opencode-ai/sdk": "^1.4.3",
         "cron-parser": "^5.0.0",
         "zod": "^4.0.0",
       },
@@ -61,8 +60,6 @@
 
     "@modelcontextprotocol/sdk": ["@modelcontextprotocol/sdk@1.29.0", "", { "dependencies": { "@hono/node-server": "^1.19.9", "ajv": "^8.17.1", "ajv-formats": "^3.0.1", "content-type": "^1.0.5", "cors": "^2.8.5", "cross-spawn": "^7.0.5", "eventsource": "^3.0.2", "eventsource-parser": "^3.0.0", "express": "^5.2.1", "express-rate-limit": "^8.2.1", "hono": "^4.11.4", "jose": "^6.1.3", "json-schema-typed": "^8.0.2", "pkce-challenge": "^5.0.0", "raw-body": "^3.0.0", "zod": "^3.25 || ^4.0", "zod-to-json-schema": "^3.25.1" }, "peerDependencies": { "@cfworker/json-schema": "^4.1.1" }, "optionalPeers": ["@cfworker/json-schema"] }, "sha512-zo37mZA9hJWpULgkRpowewez1y6ML5GsXJPY8FI0tBBCd77HEvza4jDqRKOXgHNn867PVGCyTdzqpz0izu5ZjQ=="],
 
-    "@opencode-ai/sdk": ["@opencode-ai/sdk@1.4.7", "", { "dependencies": { "cross-spawn": "7.0.6" } }, "sha512-onEtaooQyoDP5gTShQeQSf0Sd8V7949G9pPNyIyRXnVtFqyDIhUDLGtL/a/+EIW9x5s+Y6lDy/3oVoGMvQ0rQQ=="],
-
     "@types/bun": ["@types/bun@1.3.12", "", { "dependencies": { "bun-types": "1.3.12" } }, "sha512-DBv81elK+/VSwXHDlnH3Qduw+KxkTIWi7TXkAeh24zpi5l0B2kUg9Ga3tb4nJaPcOFswflgi/yAvMVBPrxMB+A=="],
 
     "@types/node": ["@types/node@22.19.17", "", { "dependencies": { "undici-types": "~6.21.0" } }, "sha512-wGdMcf+vPYM6jikpS/qhg6WiqSV/OhG+jeeHT/KlVqxYfD40iYJf9/AE1uQxVWFvU7MipKRkRv8NSHiCGgPr8Q=="],