feat: add opencode plugin for Mnemosyne routing

TypeScript plugin that injects baseURL to route Anthropic API calls
through the Mnemosyne gateway, enriches compaction with memory context,
and provides mnemosyne_status/mnemosyne_query custom tools.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

opencode-plugin/package.json

@@ -0,0 +1,46 @@
+{
+  "name": "opencode-mnemosyne",
+  "version": "0.1.0",
+  "description": "Mnemosyne context manager plugin for opencode — object-addressed memory with multi-fidelity compression",
+  "type": "module",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "default": "./dist/index.js"
+    }
+  },
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "build": "tsc",
+    "dev": "tsc --watch",
+    "prepublishOnly": "npm run build"
+  },
+  "dependencies": {
+    "@opencode-ai/plugin": "^1.0.85"
+  },
+  "devDependencies": {
+    "@types/node": "^25.5.0",
+    "typescript": "^5.7.0"
+  },
+  "opencode": {
+    "type": "plugin",
+    "hooks": [
+      "event",
+      "config",
+      "chat.message",
+      "experimental.chat.messages.transform",
+      "experimental.session.compacting",
+      "tool.execute.after"
+    ]
+  },
+  "keywords": [
+    "opencode",
+    "plugin",
+    "context-management",
+    "mnemosyne",
+    "memory"
+  ],
+  "license": "MIT"
+}