[docs] Update CLAUDE and other agent docs

[mattpodwysocki]

Description

This PR restructures the project documentation to better serve different
audiences and eliminate redundancy. The changes create clearer separation
of concerns across documentation files:

New structure:

• docs/engineering_standards.md - New comprehensive contributor
  guidelines (code quality, testing, security, common pitfalls)
• CLAUDE.md - Condensed to focus on architecture and technical patterns
  only
• AGENTS.md - Refocused on critical patterns and factual errors AI
  agents commonly make
• .github/copilot-instructions.md - Reorganized into numbered sections
  with clear priorities
• README.md - Updated contributing section to reference all
  documentation

Key improvements:

• Eliminated redundant command listings across multiple files
• Created single source of truth for engineering standards
• Made agent-focused docs more actionable with concrete examples of
  correct vs. incorrect patterns
• Improved Copilot instructions with clear priorities and "when to avoid"
  guidance
• All docs now cross-reference each other for comprehensive coverage

No functional changes - purely documentation reorganization.

Testing

• ✅ Verified all referenced file paths are correct
• ✅ Confirmed cross-references between docs work correctly
• ✅ Validated markdown formatting renders properly
• ✅ Checked that no code or configuration was modified
• ✅ Build and test commands remain unchanged"

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Checklist

• Code has been tested locally
• Unit tests have been added or updated
• Documentation has been updated if needed

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Additional Notes

[alexisraykhel]

this is confusing, can tools be either snake case or camel case? it's just important they have "tool" at the end? or do they all need to be one type?

[mattpodwysocki]

Replaced with

• Tool naming: Tool names (MCP identifiers) must be snake_case_tool (e.g., list_styles_tool). TypeScript class names follow PascalCaseTool convention (e.g., ListStylesTool)