Add .github/copilot-instructions.md for agent onboarding

[Copilot]

Adds onboarding documentation for GitHub Copilot coding agents working on Alfa for the first time.

Contents

Technical Environment

• TypeScript 5.9.3 strict mode, ES2022 target, ESM with .js import extensions required
• Node.js ≥20, Yarn 4.12.0 Berry, 80+ workspace packages in monorepo
• Vitest with coverage thresholds (75% lines, 80% branches)
• Custom TypeScript solution builder, 3-4 min build time, 8GB memory requirement

Critical Conventions

• Tests import from dist/ not src/ - must build before testing
• All packages share synchronized version number
• Changesets required for API/behavior changes: **[kind]:** [title] format
• Functional programming patterns: Option, Result, Either types throughout

Workflows Documented

• Build/test/watch commands with package-specific variants
• Changeset creation and release process
• API extraction and dependency analysis with knip
• Scratch file experimentation setup
• CI/CD integration workflow details

Troubleshooting

• Common build, test, and dependency issues
• TypeScript ESM gotchas
• Memory and performance considerations
• Package reference synchronization

Quick command reference and best practices included for efficient agent operation.

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[changeset-bot]

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Latest commit: 337ab8a

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