refactor(cli): address nuanced snapshot rendering scenarios through layout and padding refinements

- Refined height calculation logic in ToolGroupMessage to ensure consistent spacing between compact and standard tools.
- Adjusted padding and margins in StickyHeader, ToolConfirmationQueue, ShellToolMessage, and ToolMessage for visual alignment.
- Updated TOOL_RESULT_STANDARD_RESERVED_LINE_COUNT to account for internal layout changes.
- Improved ToolResultDisplay height handling in alternate buffer mode.
- Updated test snapshots to reflect layout and spacing corrections.

refactor(cli): cleanup and simplify UI components

- Reduced UI refresh delay in AppContainer.tsx for a more responsive user experience.
- Reorder imports and hook definitions within AppContainer.tsx to reduce diff 'noise'.

refactor(cli): enhance compact output robustness and visual regression testing

Addressing automated review feedback to improve code maintainability and layout stability.

1. Robust File Extension Parsing:
- Introduced getFileExtension utility in packages/cli/src/ui/utils/fileUtils.ts using node:path for reliable extension extraction.
- Updated DenseToolMessage and DiffRenderer to use the new utility, replacing fragile string splitting.

2. Visual Regression Coverage:
- Added SVG snapshot tests to DenseToolMessage.test.tsx to verify semantic color rendering and layout integrity in compact mode.

fix(cli): resolve dense tool output code quality issues

- Replaced manual string truncation with Ink's `wrap="truncate-end"` to adhere to UI guidelines.
- Added `isReadManyFilesResult` type guard to `packages/core/src/tools/tools.ts` to improve typing for structured tool results.
- Fixed an incomplete test case in `DenseToolMessage.test.tsx` to properly simulate expansion via context instead of missing mouse events.

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

@@ -222,38 +222,41 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
         !Array.isArray(prevGroup) &&
         isCompactTool(prevGroup, isCompactModeEnabled);
 
-      if (Array.isArray(group)) {
+      const isAgentGroup = Array.isArray(group);
+      const isCompact =
+        !isAgentGroup && isCompactTool(group, isCompactModeEnabled);
+
+      if (isFirst) {
+        height += (borderTopOverride ?? false) ? 1 : 0;
+      } else if (isCompact && prevIsCompact) {
+        height += 0;
+      } else if (isCompact || prevIsCompact) {
+        height += 1;
+      } else {
+        // Gap is provided by StickyHeader's paddingTop=1
+        height += 0;
+      }
+
+      const isFirstProp = !!(isFirst
+        ? (borderTopOverride ?? true)
+        : prevIsCompact);
+
+      if (isAgentGroup) {
         // Agent group
         height += 1; // Header
         height += group.length; // 1 line per agent
-        const isFirstProp = isFirst
-          ? (borderTopOverride ?? true)
-          : prevIsCompact;
         if (isFirstProp) height += 1; // Top border
-
-        // Spacing logic
-        if (isFirst) {
-          height += (borderTopOverride ?? true) ? 1 : 0;
-        } else {
-          height += 1; // marginTop
-        }
       } else {
-        const isCompact = isCompactTool(group, isCompactModeEnabled);
         if (isCompact) {
           height += 1; // Base height for compact tool
-          // Spacing logic (matching marginTop)
-          if (isFirst) {
-            height += (borderTopOverride ?? true) ? 1 : 0;
-          } else if (!prevIsCompact) {
-            height += 1;
-          }
         } else {
-          height += 3; // Static overhead for standard tool
-          if (isFirst) {
-            height += (borderTopOverride ?? true) ? 1 : 0;
-          } else {
-            height += 1; // marginTop is always 1 for non-compact tools (not first)
-          }
+          // Static overhead for standard tool header:
+          // 1 line for header text
+          // 1 line for dark separator
+          // 1 line for tool body internal paddingTop=1
+          // 1 line for top border (if isFirstProp) OR StickyHeader paddingTop=1 (if !isFirstProp)
+          height += 3;
+          height += isFirstProp ? 1 : 1; // Either top border or paddingTop
         }
       }
     }
@@ -352,12 +355,14 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
 
         let marginTop = 0;
         if (isFirst) {
-          // marginTop = (borderTopOverride ?? true) ? 1 : 0;
           marginTop = (borderTopOverride ?? false) ? 1 : 0;
         } else if (isCompact && prevIsCompact) {
           marginTop = 0;
-        } else {
+        } else if (isCompact || prevIsCompact) {
           marginTop = 1;
+        } else {
+          // Subsequent standard tools: StickyHeader's paddingTop=1 provides the gap.
+          marginTop = 0;
         }
 
         const isFirstProp = !!(isFirst