Scaffolding and Foundation Changes

- feat(cli): add compactToolOutput ui setting
- feat(cli): add DenseToolMessage component and supporting rendering logic
- feat(cli): implement compact tool output rendering logic in ToolGroupMessage
- feat(core): add tool display name constants and update tool constructors
- feat(cli): update compact output allowlist to use DISPLAY_NAME constants
- test(cli): add compact tool output rendering and spacing tests

-----
Note: Unsafe assignments/assertions/'any' usage still exist in ToolGroupMessage.tsx and DenseToolMessage.tsx and need to be addressed before PR.
Note: Tests contain 'any' casts for mocks that need to be addressed before PR.

packages/cli/src/ui/components/messages/ToolGroupMessage.compact.test.tsx

@@ -0,0 +1,135 @@
+
+import { renderWithProviders } from '../../../test-utils/render.js';
+import { ToolGroupMessage } from './ToolGroupMessage.js';
+import {
+  CoreToolCallStatus,
+  LS_DISPLAY_NAME,
+  READ_FILE_DISPLAY_NAME,
+} from '@google/gemini-cli-core';
+import { expect, it, describe } from 'vitest';
+
+describe('ToolGroupMessage Compact Rendering', () => {
+  const defaultProps = {
+    item: { 
+      id: '1', 
+      role: 'assistant', 
+      content: '', 
+      timestamp: new Date(),
+      type: 'help' as const, // Adding type property to satisfy HistoryItem type
+    },
+    terminalWidth: 80,
+  };
+
+  const compactSettings = {
+    merged: {
+      ui: {
+        compactToolOutput: true,
+      },
+    },
+  };
+
+  it('renders consecutive compact tools without empty lines between them', async () => {
+    const toolCalls = [
+      {
+        callId: 'call1',
+        name: LS_DISPLAY_NAME,
+        status: CoreToolCallStatus.Success,
+        resultDisplay: 'file1.txt\nfile2.txt',
+      },
+      {
+        callId: 'call2',
+        name: LS_DISPLAY_NAME,
+        status: CoreToolCallStatus.Success,
+        resultDisplay: 'file3.txt',
+      },
+    ];
+
+    const { lastFrame, waitUntilReady } = renderWithProviders(
+      <ToolGroupMessage {...defaultProps} toolCalls={toolCalls as any} />,
+      { settings: compactSettings as any }
+    );
+
+    await waitUntilReady();
+    const output = lastFrame();
+    
+    expect(output).toMatchSnapshot();
+  });
+
+  it('adds an empty line between a compact tool and a standard tool', async () => {
+    const toolCalls = [
+      {
+        callId: 'call1',
+        name: LS_DISPLAY_NAME,
+        status: CoreToolCallStatus.Success,
+        resultDisplay: 'file1.txt',
+      },
+      {
+        callId: 'call2',
+        name: 'non-compact-tool',
+        status: CoreToolCallStatus.Success,
+        resultDisplay: 'some large output',
+      },
+    ];
+
+    const { lastFrame, waitUntilReady } = renderWithProviders(
+      <ToolGroupMessage {...defaultProps} toolCalls={toolCalls as any} />,
+      { settings: compactSettings as any }
+    );
+
+    await waitUntilReady();
+    const output = lastFrame();
+    expect(output).toMatchSnapshot();
+  });
+
+  it('adds an empty line if a compact tool has a dense payload', async () => {
+    const toolCalls = [
+      {
+        callId: 'call1',
+        name: LS_DISPLAY_NAME,
+        status: CoreToolCallStatus.Success,
+        resultDisplay: 'file1.txt',
+      },
+      {
+        callId: 'call2',
+        name: READ_FILE_DISPLAY_NAME,
+        status: CoreToolCallStatus.Success,
+        resultDisplay: { summary: 'read file', payload: 'file content' }, // Dense payload
+      },
+    ];
+
+    const { lastFrame, waitUntilReady } = renderWithProviders(
+      <ToolGroupMessage {...defaultProps} toolCalls={toolCalls as any} />,
+      { settings: compactSettings as any }
+    );
+
+    await waitUntilReady();
+    const output = lastFrame();
+    expect(output).toMatchSnapshot();
+  });
+
+  it('adds an empty line between a standard tool and a compact tool', async () => {
+    const toolCalls = [
+      {
+        callId: 'call1',
+        name: 'non-compact-tool',
+        status: CoreToolCallStatus.Success,
+        resultDisplay: 'some large output',
+      },
+      {
+        callId: 'call2',
+        name: LS_DISPLAY_NAME,
+        status: CoreToolCallStatus.Success,
+        resultDisplay: 'file1.txt',
+      },
+    ];
+
+    const { lastFrame, waitUntilReady } = renderWithProviders(
+      <ToolGroupMessage {...defaultProps} toolCalls={toolCalls as any} />,
+      { settings: compactSettings as any }
+    );
+
+    await waitUntilReady();
+    const output = lastFrame();
+    expect(output).toMatchSnapshot();
+  });
+});