Implement first version

[JheisonMB]

Description:

Implements all v1 core functionality for texforge. From zero stubs to a fully working CLI.

What's included

Commands

• texforge new — scaffolds projects from templates (embedded general fallback + download from texforge-templates registry
• texforge check — static linter: \input, \includegraphics, \cite, \ref/\label validation, unclosed environment detection, circular \input detection
• texforge fmt — opinionated formatter with 2-space indentation, blank line normalization, verbatim/ lstlisting preservation
• texforge build — wraps tectonic with clean error parsing
• texforge template list/add/remove/validate — full template management with local cache

Infrastructure

• install.sh bundles both texforge + tectonic (pinned v0.15.0) in a single curl
• CI workflows fixed (LF line endings, correct binary name in release.yml)
• .gitattributes for consistent line endings