Import Oxide engine (Stages 0–10) under MIT license

Full project snapshot migrated to new Gitea remote without history:
engine, editor, physics, script, examples, tests, docs, and assets.
Relicensed from GPLv3 to MIT and updated repo URLs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

engine-derive/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "oxide-engine-derive"
+description = "Derive macros for Oxide's reflection system (#[derive(Reflect)])"
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+rust-version.workspace = true
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn.workspace = true
+quote.workspace = true
+proc-macro2.workspace = true