Add corex library with resource-aware execution primitives

- Implement CI workflow for formatting, linting, testing, and documentation checks.
- Create publish workflow for automated publishing to crates.io.
- Add .gitignore to exclude build artifacts and editor files.
- Define Cargo.toml for corex and corex-core with dependencies and metadata.
- Add README.md files for corex and corex-core with usage instructions and licensing.
- Implement core execution primitives: spawn_io, compute, and spawn_bg with panic isolation.
- Establish global engine context for resource management based on logical CPU cores.
- Introduce error handling for compute panics.

crates/corex-core/README.md

@@ -0,0 +1,9 @@
+# corex-core
+
+Core allocation logic, global context initialization, and execution primitives for [`corex`](https://crates.io/crates/corex).
+
+Applications should depend on the `corex` facade crate rather than this crate directly.
+
+## License
+
+Licensed under either of Apache License, Version 2.0 or MIT license at your option.