Add comprehensive GitHub Copilot instructions for Xylem repository

[Copilot]

This PR adds comprehensive GitHub Copilot coding agent instructions to help developers work effectively in the Xylem codebase. The instructions are stored in .github/copilot-instructions.md and provide detailed guidance on building, testing, and developing Gordon Beeming's personal blog.

Key Features

Exhaustively Validated Commands: Every command in the instructions has been tested and timed to ensure accuracy:

• pnpm install - 2 minutes 22 seconds (1067 packages)
• pnpm run build - 1 minute 14 seconds (processes 150 blog posts, generates 688 static pages)
• pnpm run dev - 3 seconds startup time
• pnpm run lint - 3 seconds

Manual Validation Scenarios: The instructions include specific user workflows that must be tested after changes:

• Homepage functionality with recent blog posts
• Search functionality (tested with "rust" query finding 5 posts)
• Theme switching between Light/Dark/System modes
• Blog navigation, tag filtering, and content rendering

Critical Timing Guidance: Includes explicit "NEVER CANCEL" warnings with timeout recommendations:

• Build processes require 5+ minute timeouts due to extensive content processing
• Development server startup is fast (3 seconds) but builds take time

Architecture Overview: Documents the technology stack and key components:

• Next.js 15.3.3 with React 19.1.0 and TypeScript
• Contentlayer2 for MDX content processing
• TailwindCSS for styling
• Automated RSS feed generation and search indexing

Deployment Context: Covers GitHub Actions pipeline and Docker containerization, including documented limitations in sandboxed environments due to certificate chain issues.

The instructions follow an imperative tone as requested and prioritize working commands over verbose explanations. They provide everything a GitHub Copilot agent needs to successfully work in this codebase without additional context gathering.

Fixes #102.

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✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[Copilot]

Pull Request Overview

This PR adds comprehensive GitHub Copilot coding agent instructions to help developers work effectively in the Xylem repository. The instructions provide detailed guidance on building, testing, and developing Gordon Beeming's personal blog with exhaustively validated commands and critical timing guidance.

Key changes include:

• Complete setup and development workflow documentation with validated timing data
• Manual validation scenarios and pre-commit checklists for quality assurance
• Architecture overview covering Next.js, Contentlayer2, and deployment pipeline details

Reviewed Changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 1 comment.

File	Description
.github/copilot-instructions.md	Comprehensive instructions for GitHub Copilot agents covering setup, development workflows, architecture, and troubleshooting
public/feed.xml	Updated RSS feed with new blog post entry and refreshed lastBuildDate
public/tags/*/feed.xml	Generated tag-specific RSS feeds for kata, programming, rust, software-development, and tdd tags