feat(01-04): create log directory management

- LogLevel, LogEntry, LogConfig types in types.ts
- LogManager class with directory management
- Cross-platform paths using node:os and node:path
- ensureLogDir/ensureProcessDir for directory creation
- getLogPath returns ~/.cw/logs/{processId}/{stream}.log
- cleanOldLogs removes directories older than N days
- listLogs enumerates all process log directories

src/logging/manager.ts

@@ -0,0 +1,123 @@
+/**
+ * Log Manager
+ *
+ * Manages log directories and file paths for per-process logging.
+ */
+
+import { mkdir, readdir, rm, stat } from 'node:fs/promises';
+import { homedir } from 'node:os';
+import { join } from 'node:path';
+import type { LogConfig, LogStream } from './types.js';
+
+/**
+ * Default base directory for logs: ~/.cw/logs
+ */
+const DEFAULT_LOG_DIR = join(homedir(), '.cw', 'logs');
+
+/**
+ * Manages log directory structure and file paths.
+ *
+ * Log directory structure:
+ * ~/.cw/logs/{processId}/stdout.log
+ * ~/.cw/logs/{processId}/stderr.log
+ */
+export class LogManager {
+  private readonly baseDir: string;
+  private readonly retainDays?: number;
+
+  constructor(config?: Partial<LogConfig>) {
+    this.baseDir = config?.baseDir ?? DEFAULT_LOG_DIR;
+    this.retainDays = config?.retainDays;
+  }
+
+  /**
+   * Ensures the base log directory exists.
+   * Creates it recursively if it doesn't exist.
+   */
+  async ensureLogDir(): Promise<void> {
+    await mkdir(this.baseDir, { recursive: true });
+  }
+
+  /**
+   * Ensures the process-specific log directory exists.
+   * @param processId - The process identifier
+   */
+  async ensureProcessDir(processId: string): Promise<void> {
+    const processDir = this.getProcessDir(processId);
+    await mkdir(processDir, { recursive: true });
+  }
+
+  /**
+   * Gets the directory path for a specific process's logs.
+   * @param processId - The process identifier
+   */
+  getProcessDir(processId: string): string {
+    return join(this.baseDir, processId);
+  }
+
+  /**
+   * Gets the full path to a log file for a process and stream.
+   * @param processId - The process identifier
+   * @param stream - Either 'stdout' or 'stderr'
+   */
+  getLogPath(processId: string, stream: LogStream): string {
+    return join(this.baseDir, processId, `${stream}.log`);
+  }
+
+  /**
+   * Lists all log directories (one per process).
+   * @returns Array of process IDs that have log directories
+   */
+  async listLogs(): Promise<string[]> {
+    try {
+      const entries = await readdir(this.baseDir, { withFileTypes: true });
+      return entries
+        .filter((entry) => entry.isDirectory())
+        .map((entry) => entry.name);
+    } catch (error) {
+      // If directory doesn't exist, return empty list
+      if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
+        return [];
+      }
+      throw error;
+    }
+  }
+
+  /**
+   * Removes log directories older than the specified number of days.
+   * @param retainDays - Number of days to retain logs (uses config value if not provided)
+   * @returns Number of directories removed
+   */
+  async cleanOldLogs(retainDays?: number): Promise<number> {
+    const days = retainDays ?? this.retainDays;
+    if (days === undefined) {
+      return 0;
+    }
+
+    const cutoffTime = Date.now() - days * 24 * 60 * 60 * 1000;
+    const processIds = await this.listLogs();
+    let removedCount = 0;
+
+    for (const processId of processIds) {
+      const processDir = this.getProcessDir(processId);
+      try {
+        const stats = await stat(processDir);
+        if (stats.mtime.getTime() < cutoffTime) {
+          await rm(processDir, { recursive: true, force: true });
+          removedCount++;
+        }
+      } catch {
+        // Skip if we can't stat or remove the directory
+      }
+    }
+
+    return removedCount;
+  }
+
+  /**
+   * Gets the base directory path.
+   */
+  getBaseDir(): string {
+    return this.baseDir;
+  }
+}

src/logging/types.ts

@@ -0,0 +1,41 @@
+/**
+ * Logging Types
+ *
+ * Type definitions for the file-based logging infrastructure.
+ */
+
+/**
+ * Log severity levels.
+ */
+export type LogLevel = 'debug' | 'info' | 'warn' | 'error';
+
+/**
+ * A single log entry with metadata.
+ */
+export interface LogEntry {
+  /** When this entry was logged */
+  timestamp: Date;
+  /** Severity level */
+  level: LogLevel;
+  /** ID of the process that produced this log */
+  processId: string;
+  /** The log message content */
+  message: string;
+}
+
+/**
+ * Configuration for the logging system.
+ */
+export interface LogConfig {
+  /** Base directory for log files. Defaults to ~/.cw/logs */
+  baseDir: string;
+  /** Maximum size per log file in bytes before rotation. Optional. */
+  maxFileSize?: number;
+  /** Number of days to retain logs. Optional. */
+  retainDays?: number;
+}
+
+/**
+ * Stream type for log output.
+ */
+export type LogStream = 'stdout' | 'stderr';