feat: add TypeScript declaration files for all core libraries

Add .d.ts type definitions for all four library modules:
- utils.d.ts: Platform detection, file ops, hook I/O, git helpers
- package-manager.d.ts: PM detection with PackageManagerName union type,
  DetectionSource union, and typed config interfaces
- session-manager.d.ts: Session CRUD with Session, SessionMetadata,
  SessionStats, and SessionListResult interfaces
- session-aliases.d.ts: Alias management with typed result interfaces
  for set, delete, rename, and cleanup operations

These provide IDE autocomplete and type-checking for TypeScript
consumers of the npm package without converting the source to TS.

scripts/lib/utils.d.ts

@@ -0,0 +1,169 @@
+/**
+ * Cross-platform utility functions for Claude Code hooks and scripts.
+ * Works on Windows, macOS, and Linux.
+ */
+
+import type { ExecSyncOptions } from 'child_process';
+
+// Platform detection
+export const isWindows: boolean;
+export const isMacOS: boolean;
+export const isLinux: boolean;
+
+// --- Directories ---
+
+/** Get the user's home directory (cross-platform) */
+export function getHomeDir(): string;
+
+/** Get the Claude config directory (~/.claude) */
+export function getClaudeDir(): string;
+
+/** Get the sessions directory (~/.claude/sessions) */
+export function getSessionsDir(): string;
+
+/** Get the learned skills directory (~/.claude/skills/learned) */
+export function getLearnedSkillsDir(): string;
+
+/** Get the temp directory (cross-platform) */
+export function getTempDir(): string;
+
+/**
+ * Ensure a directory exists, creating it recursively if needed.
+ * Handles EEXIST race conditions from concurrent creation.
+ * @throws If directory cannot be created (e.g., permission denied)
+ */
+export function ensureDir(dirPath: string): string;
+
+// --- Date/Time ---
+
+/** Get current date in YYYY-MM-DD format */
+export function getDateString(): string;
+
+/** Get current time in HH:MM format */
+export function getTimeString(): string;
+
+/** Get current datetime in YYYY-MM-DD HH:MM:SS format */
+export function getDateTimeString(): string;
+
+// --- Session/Project ---
+
+/**
+ * Get short session ID from CLAUDE_SESSION_ID environment variable.
+ * Returns last 8 characters, falls back to project name then the provided fallback.
+ */
+export function getSessionIdShort(fallback?: string): string;
+
+/** Get the git repository name from the current working directory */
+export function getGitRepoName(): string | null;
+
+/** Get project name from git repo or current directory basename */
+export function getProjectName(): string | null;
+
+// --- File operations ---
+
+export interface FileMatch {
+  /** Absolute path to the matching file */
+  path: string;
+  /** Modification time in milliseconds since epoch */
+  mtime: number;
+}
+
+export interface FindFilesOptions {
+  /** Maximum age in days. Only files modified within this many days are returned. */
+  maxAge?: number | null;
+  /** Whether to search subdirectories recursively */
+  recursive?: boolean;
+}
+
+/**
+ * Find files matching a glob-like pattern in a directory.
+ * Supports `*` (any chars), `?` (single char), and `.` (literal dot).
+ * Results are sorted by modification time (newest first).
+ */
+export function findFiles(dir: string, pattern: string, options?: FindFilesOptions): FileMatch[];
+
+/**
+ * Read a text file safely. Returns null if the file doesn't exist or can't be read.
+ */
+export function readFile(filePath: string): string | null;
+
+/** Write a text file, creating parent directories if needed */
+export function writeFile(filePath: string, content: string): void;
+
+/** Append to a text file, creating parent directories if needed */
+export function appendFile(filePath: string, content: string): void;
+
+/**
+ * Replace text in a file (cross-platform sed alternative).
+ * @returns true if the file was found and updated, false if file not found
+ */
+export function replaceInFile(filePath: string, search: string | RegExp, replace: string): boolean;
+
+/**
+ * Count occurrences of a pattern in a file.
+ * The global flag is enforced automatically for correct counting.
+ */
+export function countInFile(filePath: string, pattern: string | RegExp): number;
+
+export interface GrepMatch {
+  /** 1-based line number */
+  lineNumber: number;
+  /** Full content of the matching line */
+  content: string;
+}
+
+/** Search for a pattern in a file and return matching lines with line numbers */
+export function grepFile(filePath: string, pattern: string | RegExp): GrepMatch[];
+
+// --- Hook I/O ---
+
+export interface ReadStdinJsonOptions {
+  /**
+   * Timeout in milliseconds. Prevents hooks from hanging indefinitely
+   * if stdin never closes. Default: 5000
+   */
+  timeoutMs?: number;
+}
+
+/**
+ * Read JSON from stdin (for hook input).
+ * Returns an empty object if stdin is empty or times out.
+ */
+export function readStdinJson(options?: ReadStdinJsonOptions): Promise<Record<string, unknown>>;
+
+/** Log a message to stderr (visible to user in Claude Code terminal) */
+export function log(message: string): void;
+
+/** Output data to stdout (returned to Claude's context) */
+export function output(data: string | Record<string, unknown>): void;
+
+// --- System ---
+
+/**
+ * Check if a command exists in PATH.
+ * Only allows alphanumeric, dash, underscore, and dot characters.
+ * WARNING: Spawns a child process (where.exe on Windows, which on Unix).
+ */
+export function commandExists(cmd: string): boolean;
+
+export interface CommandResult {
+  success: boolean;
+  /** Trimmed stdout on success, stderr or error message on failure */
+  output: string;
+}
+
+/**
+ * Run a shell command and return the output.
+ * SECURITY: Only use with trusted, hardcoded commands.
+ * Never pass user-controlled input directly.
+ */
+export function runCommand(cmd: string, options?: ExecSyncOptions): CommandResult;
+
+/** Check if the current directory is inside a git repository */
+export function isGitRepo(): boolean;
+
+/**
+ * Get git modified files (staged + unstaged), optionally filtered by regex patterns.
+ * Invalid regex patterns are silently skipped.
+ */
+export function getGitModifiedFiles(patterns?: string[]): string[];