feat: implement Phase 9 - Keyboard Shortcuts

Features added:
- Created useKeyboardShortcuts hook for managing keyboard shortcuts
  - Supports modifier keys (Ctrl, Shift, Alt)
  - Automatically ignores shortcuts when input fields are focused
  - ESC key blurs input fields to enable shortcuts
- Added global keyboard shortcuts:
  - / : Focus search field
  - r : Refresh process list
  - a : Select all processes (flat view only)
  - ESC : Clear selection / unfocus
  - ? (Shift+/) : Show keyboard shortcuts help
- Added process navigation shortcuts:
  - j : Select next process
  - k : Select previous process
  - Space : Toggle selection of focused process
  - Auto-scroll to focused process
- Created KeyboardShortcutsHelp modal component:
  - Organized shortcuts by category
  - Visual kbd elements for keys
  - Info about input field behavior
- Added keyboard shortcuts button to processes page header
- Added isFocused prop to ProcessCard with accent ring styling
- Added data-process-id attributes for keyboard navigation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/hooks/useKeyboardShortcuts.ts

@@ -0,0 +1,88 @@
+import { useEffect, useCallback } from 'react';
+
+export interface KeyboardShortcut {
+  key: string;
+  ctrl?: boolean;
+  shift?: boolean;
+  alt?: boolean;
+  description: string;
+  action: () => void;
+  enabled?: boolean;
+}
+
+export interface UseKeyboardShortcutsOptions {
+  shortcuts: KeyboardShortcut[];
+  ignoreWhenInputFocused?: boolean;
+}
+
+/**
+ * Hook for managing keyboard shortcuts
+ * Automatically handles event listeners and cleanup
+ */
+export function useKeyboardShortcuts({
+  shortcuts,
+  ignoreWhenInputFocused = true,
+}: UseKeyboardShortcutsOptions) {
+  const handleKeyDown = useCallback(
+    (event: KeyboardEvent) => {
+      // Ignore if typing in input/textarea/select
+      if (ignoreWhenInputFocused) {
+        const target = event.target as HTMLElement;
+        const tagName = target.tagName.toLowerCase();
+        const isEditable = target.isContentEditable;
+
+        if (
+          tagName === 'input' ||
+          tagName === 'textarea' ||
+          tagName === 'select' ||
+          isEditable
+        ) {
+          // Allow ESC to blur inputs
+          if (event.key === 'Escape') {
+            target.blur();
+          }
+          return;
+        }
+      }
+
+      // Find matching shortcut
+      for (const shortcut of shortcuts) {
+        if (shortcut.enabled === false) continue;
+
+        const keyMatches = event.key.toLowerCase() === shortcut.key.toLowerCase();
+        const ctrlMatches = shortcut.ctrl ? event.ctrlKey || event.metaKey : !event.ctrlKey && !event.metaKey;
+        const shiftMatches = shortcut.shift ? event.shiftKey : !event.shiftKey;
+        const altMatches = shortcut.alt ? event.altKey : !event.altKey;
+
+        if (keyMatches && ctrlMatches && shiftMatches && altMatches) {
+          event.preventDefault();
+          shortcut.action();
+          break;
+        }
+      }
+    },
+    [shortcuts, ignoreWhenInputFocused]
+  );
+
+  useEffect(() => {
+    window.addEventListener('keydown', handleKeyDown);
+    return () => window.removeEventListener('keydown', handleKeyDown);
+  }, [handleKeyDown]);
+}
+
+/**
+ * Common keyboard shortcuts for reference
+ */
+export const COMMON_SHORTCUTS = {
+  SEARCH: { key: '/', description: 'Focus search' },
+  REFRESH: { key: 'r', description: 'Refresh data' },
+  SELECT_ALL: { key: 'a', description: 'Select all' },
+  ESCAPE: { key: 'Escape', description: 'Clear selection / Close modal' },
+  HELP: { key: '?', shift: true, description: 'Show keyboard shortcuts' },
+  NEXT: { key: 'j', description: 'Next item' },
+  PREVIOUS: { key: 'k', description: 'Previous item' },
+  SELECT: { key: ' ', description: 'Toggle selection' },
+  START: { key: 's', description: 'Start selected' },
+  STOP: { key: 'x', description: 'Stop selected' },
+  RESTART: { key: 't', description: 'Restart selected' },
+} as const;