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/adapters/claude-local/src/index.ts

@@ -0,0 +1,8 @@
+export const type = "claude_local";
+export const label = "Claude Code (local)";
+
+export const models = [
+  { id: "claude-opus-4-6", label: "Claude Opus 4.6" },
+  { id: "claude-sonnet-4-5-20250929", label: "Claude Sonnet 4.5" },
+  { id: "claude-haiku-4-5-20251001", label: "Claude Haiku 4.5" },
+];