`router-core` `update_metadata` emits `metadata_updated` event without including the new metadata value

[Maki-Zeninn]

Bug

env.events().publish(
    (Symbol::new(&env, "metadata_updated"),),
    name.clone(),   // ← only route name, no metadata value
);

Fix

Include the new metadata in the event payload:

env.events().publish(
    (Symbol::new(&env, "metadata_updated"),),
    (name.clone(), metadata.clone()),
);

If including the full Option<RouteMetadata> is too large, include a boolean has_metadata:

(name.clone(), metadata.is_some()),

Tests to add

1. test_metadata_updated_event_includes_metadata — set metadata, assert event data contains the new value

[Emins25]

I put together a fix for this.

Summary:

• included the updated metadata value in the metadata_updated event payload
• preserved the stored metadata update behavior
• added regression coverage for the emitted event payload

PR: #200