refactor: modularize CCS architecture - Phase 02 complete

Split monolithic ccs.ts (1071 lines) into modular command handlers:

Main file reduction:
- ccs.ts: 1071 → 593 lines (44.6% reduction)
- Maintains routing logic + profile detection + GLMT proxy

New utility modules:
- src/utils/shell-executor.ts: Cross-platform shell execution
- src/utils/package-manager-detector.ts: Package manager detection

New command handlers:
- src/commands/version-command.ts: Version display
- src/commands/help-command.ts: Help text and usage
- src/commands/install-command.ts: Install/uninstall stubs
- src/commands/doctor-command.ts: Health checks
- src/commands/sync-command.ts: CCS synchronization
- src/commands/shell-completion-command.ts: Shell completion

Validation:
- 39/39 tests passing (100% success rate)
- TypeScript compilation: ✅ Zero errors
- ESLint: ✅ Zero violations
- Manual testing: ✅ All commands working

Code review: EXCELLENT rating, 0 critical issues, zero regressions

Tier1 plan: 2/2 phases complete - both ESLint strictness and
modular architecture successfully implemented.

src/utils/shell-executor.ts

@@ -0,0 +1,59 @@
+/**
+ * Shell Executor Utilities
+ *
+ * Cross-platform shell execution utilities for CCS.
+ */
+
+import { spawn, ChildProcess } from 'child_process';
+import { ErrorManager } from './error-manager';
+
+/**
+ * Escape arguments for shell execution (Windows compatibility)
+ */
+export function escapeShellArg(arg: string): string {
+  return '"' + String(arg).replace(/"/g, '""') + '"';
+}
+
+/**
+ * Execute Claude CLI with unified spawn logic
+ */
+export function execClaude(
+  claudeCli: string,
+  args: string[],
+  envVars: NodeJS.ProcessEnv | null = null
+): void {
+  const isWindows = process.platform === 'win32';
+  const needsShell = isWindows && /\.(cmd|bat|ps1)$/i.test(claudeCli);
+
+  // Prepare environment (merge with process.env if envVars provided)
+  const env = envVars ? { ...process.env, ...envVars } : process.env;
+
+  let child: ChildProcess;
+  if (needsShell) {
+    // When shell needed: concatenate into string to avoid DEP0190 warning
+    const cmdString = [claudeCli, ...args].map(escapeShellArg).join(' ');
+    child = spawn(cmdString, {
+      stdio: 'inherit',
+      windowsHide: true,
+      shell: true,
+      env,
+    });
+  } else {
+    // When no shell needed: use array form (faster, no shell overhead)
+    child = spawn(claudeCli, args, {
+      stdio: 'inherit',
+      windowsHide: true,
+      env,
+    });
+  }
+
+  child.on('exit', (code, signal) => {
+    if (signal) process.kill(process.pid, signal as NodeJS.Signals);
+    else process.exit(code || 0);
+  });
+
+  child.on('error', () => {
+    ErrorManager.showClaudeNotFound();
+    process.exit(1);
+  });
+}