Initial boilerplate scaffold for continuum-common

Adds ts-core (logger, Supabase JWT verification, Elysia error
transformers) and rust-core (thiserror error type, tracing init,
G-code checksum/header parsing) packages.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -0,0 +1,15 @@
+{
+  "name": "continuum-common",
+  "private": true,
+  "version": "0.1.0",
+  "workspaces": [
+    "packages/ts-core"
+  ],
+  "scripts": {
+    "build": "bun run --filter '*' build",
+    "typecheck": "bun run --filter '*' typecheck"
+  },
+  "engines": {
+    "bun": ">=1.1.0"
+  }
+}