Move adapter implementations into shared workspace packages

Extract claude-local and codex-local adapter code from cli/server/ui
into packages/adapters/ and packages/adapter-utils/. CLI, server, and
UI now import shared adapter logic instead of duplicating it. Removes
~1100 lines of duplicated code across packages. Register new packages
in pnpm workspace.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/adapter-utils/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "@paperclip/adapter-utils",
+  "version": "0.0.1",
+  "private": true,
+  "type": "module",
+  "exports": {
+    ".": "./src/index.ts",
+    "./*": "./src/*.ts"
+  },
+  "scripts": {
+    "typecheck": "tsc --noEmit"
+  },
+  "devDependencies": {
+    "typescript": "^5.7.3"
+  }
+}