Add Challenge Archive pages with October 2025 challenge summary

Challenge-Archive.md

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+[← Back to Home Page](Home)
+
+# Challenge Archive
+
+## Table of Contents
+
+- [About the Archive](#about-the-archive)
+- [Past Challenges](#past-challenges)
+
+## About the Archive
+
+Welcome to the Challenge Archive! Here you'll find summaries of all past monthly 3D printing challenges from the Fargo 3D Print Meetup. Each challenge page includes an overview, key details, and links to the complete challenge information in the main repository.
+
+## Past Challenges
+
+### 2025
+
+- **[October 2025: "Is it Glass or Clearly Natural?"](October-2025)** - Transparency challenge using 3D Fuel's Clearly Natural filament

October-2025.md

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+[← Back to Challenge Archive](Challenge-Archive)
+
+# October 2025 Challenge
+
+## Table of Contents
+
+- [Challenge Title](#challenge-title)
+- [Overview](#overview)
+- [Key Details](#key-details)
+- [Competition Categories](#competition-categories)
+- [Results](#results)
+- [Full Challenge Details](#full-challenge-details)
+
+## Challenge Title
+
+**"Is it Glass or Clearly Natural?"**
+
+## Overview
+
+Experience the clarity of 3D Fuel's "Clearly Natural" filament in this transparency-focused challenge! Participants attempted to create the clearest possible print, testing the limits of clear filament printing techniques.
+
+The challenge involved printing a simple cylinder (25mm diameter x 50mm height) in vase mode using 3D Fuel's Clearly Natural filament, available in both PCTG and PLA variants.
+
+## Key Details
+
+- **Challenge Period**: October 1 - October 28, 2025
+- **Material**: 3D Fuel "Clearly Natural" (PCTG or PLA)
+- **Model**: Cylinder - 25mm diameter x 50mm height
+- **Print Mode**: Vase mode (single perimeter wall)
+- **Filament Usage**: Approximately 6 grams per print
+
+## Competition Categories
+
+- **PCTG Division**: For prints using Clearly Natural PCTG
+- **PLA Division**: For prints using Clearly Natural PLA
+- **Overall Winner**: Best clarity across both divisions
+- **People's Choice Award**: Community favorite
+- **Innovation Award**: Most creative clarity technique
+
+## Results
+
+Winners were announced at the October 31, 2025 meetup.
+
+## Full Challenge Details
+
+For complete challenge information, rules, judging criteria, and model files, visit:
+
+**[October 2025 Challenge Repository](https://meetup.fargo3d.com/Fargo3d/3DPrintMeetup/src/branch/master/challenges/October-2025)**