feat: make plugin manifest required

All plugins must now declare a static manifest property with their
metadata and resource requirements. This simplifies the manifest loader
and provides better error messages.

Signed-off-by: Mario Cadenas <mario.cadenas@databricks.com>

Author: MarioCadenas

packages/shared/src/plugin.ts

@@ -47,8 +47,8 @@ export interface PluginConfig {
 export type PluginPhase = "core" | "normal" | "deferred";
 
 /**
- * Plugin constructor with optional manifest and resource requirement declaration.
- * Both manifest and getResourceRequirements are optional for backward compatibility.
+ * Plugin constructor with required manifest declaration.
+ * All plugins must declare a manifest with their metadata and resource requirements.
  */
 export type PluginConstructor<
   C = BasePluginConfig,
@@ -60,9 +60,9 @@ export type PluginConstructor<
   phase?: PluginPhase;
   /**
    * Static manifest declaring plugin metadata and resource requirements.
-   * This is the preferred way to declare resources for all plugins.
+   * Required for all plugins.
    */
-  manifest?: PluginManifest;
+  manifest: PluginManifest;
   /**
    * Optional runtime resource requirements based on config.
    * Use this when resource requirements depend on plugin configuration.