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/Cargo.toml

@@ -0,0 +1,31 @@
+[package]
+name = "corex-core"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+repository.workspace = true
+homepage.workspace = true
+documentation.workspace = true
+authors.workspace = true
+description = "Core allocation logic and execution primitives for corex."
+readme = "README.md"
+keywords = ["async", "concurrency", "rayon", "tokio", "resource-management"]
+categories = ["asynchronous", "concurrency", "rust-patterns"]
+
+[features]
+default = []
+io = ["dep:tokio"]
+compute = ["dep:rayon"]
+bg = ["dep:tokio"]
+full = ["io", "compute", "bg"]
+
+[dependencies]
+tokio = { workspace = true, optional = true }
+rayon = { workspace = true, optional = true }
+num_cpus = { workspace = true }
+tracing = { workspace = true }
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]