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, 10 insertions, 0 deletions

diff --git a/examples/example-metadata/page.toml b/examples/example-metadata/page.toml
new file mode 100644
index 0000000..1a99048
--- /dev/null
+++ b/examples/example-metadata/page.toml
@@ -0,0 +1,10 @@
+[example]
+id = "example-metadata"
+name = "Entry Metadata"
+icon = "🏷️"
+category = "advanced"
+desc = """
+Demonstrates attaching arbitrary, compile-time-typed metadata to an entry via `#[metadata(Entry)]` and retrieving it at runtime with `ProgramCollect::get_metadata`. No `pathf` needed here — everything lives in a single module.
+"""
+tags = ["metadata", "get_metadata", "extras"]
+files = ["src/main.rs", "Cargo.toml"]