feat(crdt): add @robonen/crdt package

Hand-built CRDT primitives: Lamport clock + version vectors, op-log,
LWW register/map, RGA sequence, fractional indexing, marks store, sync
encode, and doc/replica. Includes eslint flat config + composite tsconfig.

core/crdt/package.json

@@ -0,0 +1,54 @@
+{
+  "name": "@robonen/crdt",
+  "version": "0.0.1",
+  "license": "Apache-2.0",
+  "description": "Framework-agnostic CRDT primitives: RGA sequence, LWW registers, fractional indexing, version vectors",
+  "keywords": [
+    "crdt",
+    "rga",
+    "lww",
+    "collaborative",
+    "fractional-indexing",
+    "tools"
+  ],
+  "author": "Robonen Andrew <robonenandrew@gmail.com>",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/robonen/tools.git",
+    "directory": "core/crdt"
+  },
+  "packageManager": "pnpm@10.30.3",
+  "engines": {
+    "node": ">=24.13.1"
+  },
+  "type": "module",
+  "files": [
+    "dist"
+  ],
+  "exports": {
+    ".": {
+      "import": {
+        "types": "./dist/index.d.mts",
+        "default": "./dist/index.mjs"
+      },
+      "require": {
+        "types": "./dist/index.d.cts",
+        "default": "./dist/index.cjs"
+      }
+    }
+  },
+  "scripts": {
+    "lint:check": "eslint .",
+    "lint:fix": "eslint . --fix",
+    "test": "vitest run",
+    "dev": "vitest dev",
+    "build": "tsdown"
+  },
+  "devDependencies": {
+    "@robonen/eslint": "workspace:*",
+    "@robonen/tsconfig": "workspace:*",
+    "@robonen/tsdown": "workspace:*",
+    "eslint": "catalog:",
+    "tsdown": "catalog:"
+  }
+}