release: v1.15.0

[sonukapoor]

Summary

• Bump version to 1.15.0 in package.json, package-lock.json, and website/docusaurus.config.ts
• CHANGELOG entry covering all changes since v1.14.0

What's in this release

Added

• --json output now saves to a timestamped file; banner and spinner no longer suppressed in JSON mode
• install-skill subcommand writes AI assistant skill files for Claude Code, Codex CLI, Gemini CLI, Cursor, and GitHub Copilot

Fixed

• Transitive parent-upgrade guidance marks commands as path-specific when they only cover a subset of dependency paths
• pnpm lockfile traversal preserves multiple dependency paths for repeated package versions

Changed

• Dedicated caching guide covering TTL, false negative risk, and --no-cache behavior

Validation

• npm test — 233 passed
• npm run build — clean