refactor(errors): centralize error handling infrastructure

- add errors/ directory with error types, handler, cleanup registry

- extract claude-spawner.ts from auth modules

- update imports across auth, ccs, web-server

Phase 2 & 4: Error handling consolidation

src/utils/claude-spawner.ts

@@ -0,0 +1,139 @@
+/**
+ * Claude Spawner Utilities
+ *
+ * Cross-platform Claude CLI spawn utilities for CCS.
+ * Handles Windows .cmd/.bat/.ps1 files properly.
+ */
+
+import { spawn, ChildProcess, SpawnOptions } from 'child_process';
+import { escapeShellArg } from './shell-executor';
+import { getClaudeCliInfo } from './claude-detector';
+import { ErrorManager } from './error-manager';
+
+export interface SpawnClaudeOptions {
+  /** Arguments to pass to Claude CLI */
+  args?: string[];
+  /** Environment variables to merge with process.env */
+  env?: NodeJS.ProcessEnv;
+  /** Working directory */
+  cwd?: string;
+  /** Stdio configuration (default: 'inherit') */
+  stdio?: SpawnOptions['stdio'];
+}
+
+export interface SpawnClaudeResult {
+  /** The spawned child process */
+  child: ChildProcess;
+  /** Path to the Claude CLI executable */
+  claudePath: string;
+}
+
+/**
+ * Spawn Claude CLI with cross-platform support.
+ *
+ * Handles Windows .cmd/.bat/.ps1 wrappers automatically.
+ * Returns the ChildProcess for custom event handling.
+ *
+ * @throws Error if Claude CLI is not found
+ */
+export function spawnClaude(options: SpawnClaudeOptions = {}): SpawnClaudeResult {
+  const claudeInfo = getClaudeCliInfo();
+  if (!claudeInfo) {
+    throw new Error('Claude CLI not found');
+  }
+
+  const { path: claudeCli, needsShell } = claudeInfo;
+  const { args = [], env, cwd, stdio = 'inherit' } = options;
+
+  // Merge environment
+  const mergedEnv = env ? { ...process.env, ...env } : process.env;
+
+  let child: ChildProcess;
+  if (needsShell) {
+    // Windows .cmd/.bat/.ps1: concatenate into string to avoid DEP0190 warning
+    const cmdString = [claudeCli, ...args].map(escapeShellArg).join(' ');
+    child = spawn(cmdString, {
+      stdio,
+      windowsHide: true,
+      shell: true,
+      env: mergedEnv,
+      cwd,
+    });
+  } else {
+    // Unix or Windows native: use array form (faster, no shell overhead)
+    child = spawn(claudeCli, args, {
+      stdio,
+      windowsHide: true,
+      env: mergedEnv,
+      cwd,
+    });
+  }
+
+  return { child, claudePath: claudeCli };
+}
+
+/**
+ * Spawn Claude CLI and wait for exit.
+ *
+ * Convenience function that returns a promise resolving to the exit code.
+ */
+export function spawnClaudeSync(options: SpawnClaudeOptions = {}): Promise<number> {
+  return new Promise((resolve, reject) => {
+    try {
+      const { child } = spawnClaude(options);
+
+      child.on('exit', (code) => {
+        resolve(code ?? 0);
+      });
+
+      child.on('error', (error) => {
+        reject(error);
+      });
+    } catch (error) {
+      reject(error);
+    }
+  });
+}
+
+/**
+ * Spawn Claude CLI with automatic exit handling.
+ *
+ * Exits the current process when Claude exits, preserving exit code/signal.
+ * Used for simple pass-through scenarios.
+ */
+export function execClaudeWithExitHandling(options: SpawnClaudeOptions = {}): void {
+  let result: SpawnClaudeResult;
+
+  try {
+    result = spawnClaude(options);
+  } catch {
+    // Claude not found - show error and exit
+    void ErrorManager.showClaudeNotFound();
+    process.exit(1);
+  }
+
+  const { child } = result;
+
+  child.on('exit', (code, signal) => {
+    if (signal) {
+      process.kill(process.pid, signal as NodeJS.Signals);
+    } else {
+      process.exit(code ?? 0);
+    }
+  });
+
+  child.on('error', async () => {
+    await ErrorManager.showClaudeNotFound();
+    process.exit(1);
+  });
+}
+
+/**
+ * Check if shell execution is needed for a given path.
+ *
+ * Returns true for Windows .cmd/.bat/.ps1 files.
+ */
+export function needsShellExecution(executablePath: string): boolean {
+  const isWindows = process.platform === 'win32';
+  return isWindows && /\.(cmd|bat|ps1)$/i.test(executablePath);
+}