Rename crate to mytheclipse and flatten workspace to single crate

- Rename corex -> mytheclipse (corex name taken on crates.io by an
  unrelated crate published by David-Kunz in 2023)
- Flatten corex + corex-core workspace into a single crate; all modules
  (context/error/io/compute/bg) now live directly under src/
- Update Cargo.toml metadata: real repo URL, docs.rs, author
- Update README, example, doc comments, tracing span names
- Fix CI: single package dry-run (corex-core no longer separate)
- Fix publish workflow: single cargo publish step

src/error.rs

@@ -0,0 +1,28 @@
+//! Shared error type for mytheclipse execution primitives.
+
+/// Errors surfaced by mytheclipse's panic-isolated execution primitives.
+///
+/// Marked `#[non_exhaustive]` so new variants can be added without a
+/// breaking change; downstream `match` expressions should include a
+/// wildcard arm.
+#[non_exhaustive]
+#[derive(Debug)]
+pub enum CorexError {
+    /// A closure submitted to [`crate::compute::compute`] panicked.
+    ///
+    /// The contained string is a best-effort rendering of the panic
+    /// payload; the compute thread pool itself remains usable afterward.
+    ComputePanic(String),
+}
+
+impl std::fmt::Display for CorexError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::ComputePanic(message) => {
+                write!(f, "compute closure panicked: {message}")
+            }
+        }
+    }
+}
+
+impl std::error::Error for CorexError {}