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>

packages/ts-core/src/index.ts

@@ -0,0 +1,3 @@
+export * from "./logger";
+export * from "./auth";
+export * from "./errors";