fix(test): update plugin tests to use getAgentListDisplayName for agent assertions

- Update plugin-interface.test.ts expectations to use getAgentListDisplayName
- Update chat-message.test.ts expectations for agent display names
- Add smoke test for quoted plan name resolution in chat-message.test.ts
- Aligns test expectations with proper agent name formatting

🤖 Generated with OhMyOpenCode assistance

src/plugin-interface.test.ts

@@ -165,7 +165,7 @@ describe("createPluginInterface - command.execute.before", () => {
     )
 
     // then
-    expect(output.message.agent).toBe("atlas")
+    expect(output.message.agent).toBe(getAgentListDisplayName("atlas"))
     expect(getSessionAgent("ses-command-atlas")).toBe("atlas")
     expect(readBoulderState(testDir)?.agent).toBe("atlas")
   })