feat: add entry metadata system with compile-time typed values

Add `Metadata<B>` trait and `#[metadata(Entry)]` attribute macro
to attach arbitrary, compile-time-typed metadata to entries.
Implement `ProgramCollect::get_metadata<T>()` for runtime retrieval,
backed by a global registry populated by `register_metadata!`.

Extend `pathf` with `MetadataPattern` to resolve metadata types
across modules at build time. Add two examples demonstrating
metadata usage with and without pathf integration.

1 files changed, 33 insertions, 0 deletions

diff --git a/examples/example-combine-pathf-metadata/src/main.rs b/examples/example-combine-pathf-metadata/src/main.rs
new file mode 100644
index 0000000..a68eac5
--- /dev/null
+++ b/examples/example-combine-pathf-metadata/src/main.rs
@@ -0,0 +1,33 @@
+//! Example: Combining pathf + entry metadata
+//!
+//! > Demonstrates combining the `pathf` feature with entry metadata. The metadata
+//! > `DataType` (`Description`) and the dispatchers/entries are defined in the `sub`
+//! > module. Thanks to `pathf`, `gen_program!()` resolves these types across
+//! > modules automatically, so `main` stays minimal.
+//!
+//! Run:
+//! ```bash
+//! cargo run --manifest-path examples/example-combine-pathf-metadata/Cargo.toml --quiet -- hello Alice
+//! cargo run --manifest-path examples/example-combine-pathf-metadata/Cargo.toml --quiet -- hello
+//! cargo run --manifest-path examples/example-combine-pathf-metadata/Cargo.toml --quiet -- desc
+//! ```
+//!
+//! Output:
+//! ```plaintext
+//! Hello, Alice!
+//! Hello, World!
+//! EntryHello desc = okay
+//! ```
+
+mod sub;
+
+use mingling::prelude::*;
+
+fn main() {
+    let mut program = ThisProgram::new();
+    program.with_dispatcher(sub::CMDHello);
+    program.with_dispatcher(sub::CMDDescription);
+    program.exec_and_exit();
+}
+
+gen_program!();