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/rust-core/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "continuum-core"
+version = "0.1.0"
+edition = "2021"
+description = "Shared error handling, tracing setup, and G-code helpers for Continuum Rust services"
+
+[dependencies]
+thiserror = "1.0"
+anyhow = "1.0"
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
+
+[dev-dependencies]