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>

server/package.json

@@ -10,6 +10,9 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
+    "@paperclip/adapter-claude-local": "workspace:*",
+    "@paperclip/adapter-codex-local": "workspace:*",
+    "@paperclip/adapter-utils": "workspace:*",
     "@paperclip/db": "workspace:*",
     "@paperclip/shared": "workspace:*",
     "detect-port": "^2.1.0",