feat(plugins): update plugin format to new entry_point + [[providers]] style

- owlry-core/manifest: add entry_point alias for entry field, add ProviderSpec
  struct for [[providers]] array, change default entry to main.lua
- owlry-lua/manifest: add ProviderDecl struct and providers: Vec<ProviderDecl>
  for [[providers]] support
- owlry-lua/loader: fall back to manifest [[providers]] when script has no API
  registrations; fall back to global refresh() for manifest-declared providers
- owlry-lua/api: expose call_global_refresh() that calls the top-level Lua
  refresh() function directly
- owlry/plugin_commands: update create templates to emit new format:
  entry_point instead of entry, [[providers]] instead of [provides],
  main.rn/main.lua instead of init.rn/init.lua, Rune uses Item::new() builder
  pattern, Lua uses standalone refresh() function
- cmd_validate: accept [[providers]] declarations as a valid provides source

crates/owlry-lua/src/api/provider.rs

@@ -76,6 +76,15 @@ fn register_provider(lua: &Lua, config: Table) -> LuaResult<()> {
     Ok(())
 }
 
+/// Call the top-level `refresh()` global function (for manifest-declared providers)
+pub fn call_global_refresh(lua: &Lua) -> LuaResult<Vec<PluginItem>> {
+    let globals = lua.globals();
+    match globals.get::<Function>("refresh") {
+        Ok(refresh_fn) => parse_items_result(refresh_fn.call(())?),
+        Err(_) => Ok(Vec::new()),
+    }
+}
+
 /// Get all registered providers
 pub fn get_registrations(lua: &Lua) -> LuaResult<Vec<ProviderRegistration>> {
     // Suppress unused warning