refactor: rename OhMyOpenCode types to OhMyOpenAgent and centralize PACKAGE_NAME

- Rename all PascalCase types: OhMyOpenCodePlugin → OhMyOpenAgentPlugin, etc.
- 231 OhMyOpenAgent references across ~60 files
- Centralize 4 PACKAGE_NAME constants to import from plugin-identity.ts
- Update src/plugin-config.ts to use CONFIG_BASENAME from plugin-identity

Wave 3 Tasks 5 & 6 complete.

src/plugin-handlers/command-config-handler.ts

@@ -1,4 +1,4 @@
-import type { OhMyOpenCodeConfig } from "../config";
+import type { OhMyOpenAgentConfig } from "../config";
 import { getAgentDisplayName } from "../shared/agent-display-names";
 import {
   loadUserCommands,
@@ -19,7 +19,7 @@ import type { PluginComponents } from "./plugin-components-loader";
 
 export async function applyCommandConfig(params: {
   config: Record<string, unknown>;
-  pluginConfig: OhMyOpenCodeConfig;
+  pluginConfig: OhMyOpenAgentConfig;
   ctx: { directory: string };
   pluginComponents: PluginComponents;
 }): Promise<void> {