Add comprehensive LLTD automata specification document (#9)

* Add comprehensive LLTD automata specification document

This document provides detailed specification for the three LLTD finite state
machines:

1. Mapping Engine State - Handles topology discovery and mapping operations
2. Enumeration Engine State - Manages network station enumeration
3. Session Table State - Tracks per-session states

Includes:
- Complete state diagrams in Mermaid format
- Detailed transition tables for all state machines
- RepeatBand algorithm description with constants
- Implementation considerations (thread safety, timeouts, memory management)
- Protocol compliance guidelines

This documentation will serve as the reference for implementing the automata
in lltdAutomata.c.

* Fix Mermaid syntax for GitHub rendering compatibility

Corrected all three state diagrams to use proper Mermaid syntax:
- Added quotes around all edge labels to avoid parsing errors
- Replaced parentheses with hyphens in labels (e.g., "(ignore)" → "- ignore")
- Fixed issue where GitHub Mermaid parser failed on special characters

All diagrams now render correctly on GitHub.

* Improve dark mode visibility for state diagrams

Changed normal transition lines from black (#000) to blue (#1f77b4):
- Black lines were invisible on GitHub dark mode
- Blue provides good contrast on both light and dark themes
- Updated legend and all diagram comments to reflect "thick blue lines"

All three state machines (Mapping Engine, Enumeration Engine, Session Table)
now render correctly on both GitHub light and dark modes.

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Co-authored-by: Claude <noreply@anthropic.com>

Author: d3vi1