feat: migrate docs to mdBook, add cross-platform support, and publish 17 module pages

[maruf-pfc]

Overview

This PR is a major documentation and cross-platform overhaul of Aliaskit, covering three key areas: a full migration from Jekyll to mdBook, comprehensive per-module documentation across all 17 modules, and native cross-platform compatibility for Linux, macOS, and WSL/Windows.

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🗂️ Documentation: Jekyll → mdBook Migration

Replaced the GitHub Pages Jekyll configuration with a proper mdBook static site, using the mdbook-template preprocessor for dynamic module footers.

New files:

• book.toml — mdBook project config pointing to docs/src/
• docs/src/SUMMARY.md — Sidebar navigation for all 17 module chapters + Contributing guide
• docs/src/templates/footer.md — Reusable footer injected into every module page via {{#template}}
• .github/workflows/mdbook.yml — CI/CD that auto-downloads mdbook + mdbook-template binaries and deploys to GitHub Pages on every push to main

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📚 Documentation: 17 Comprehensive Module Pages

Every module now has its own dedicated chapter in docs/src/modules/, each containing:

• Full alias/function reference with description, usage signature, and shell output examples
• Platform-specific notes and tips where relevant
• Injected footer via mdbook-template

Modules documented: navigation, files, system, process, packages, network, git, docker, python, node, dotnet, cpp_java, archives, editors, servers, ssh, productivity

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🌐 Cross-Platform Support

Aliaskit now officially supports Linux, macOS, and WSL/Windows with targeted fixes rather than a full rewrite.

core/init.sh — OS Detection

Added $AK_OS environment variable exported at load time:

AK_OS="linux"   # Default Linux
AK_OS="macos"   # Darwin / macOS
AK_OS="wsl"     # Windows Subsystem for Linux
AK_OS="windows" # Git Bash / MINGW / Cygwin