Fix documentation inaccuracies about C API error handling

[Copilot]

Description of Change

Documentation incorrectly claimed the C API layer implements an "exception firewall" with try-catch blocks and defensive null checks. Code inspection revealed the C API is a minimal pass-through wrapper with no exception handling.

Corrections Made:

• Error handling claims: Removed all references to "exception firewall" and defensive null checks

  • Changed: "C API catches all C++ exceptions" → "C API is minimal wrapper, trusts C# validation"
  • Removed: Code examples showing if (!canvas || !paint) return; defensive checks
  • Actual implementation: Direct pass-through with zero try-catch blocks

• Architecture descriptions: Updated layer responsibility descriptions

  • C API: Minimal wrapper that trusts C# validation
  • C#: Safety boundary where ALL validation occurs

Files Updated:

• AGENTS.md
• design/architecture-overview.md
• design/QUICKSTART.md
• design/README.md
• design/adding-new-apis.md
• design/error-handling.md
• .github/instructions/README.md

Verified Accurate:

• Memory management patterns (ref counting, pointer types)
• C# validation patterns
• Threading claims
• File paths and build commands
• Code examples

Bugs Fixed

None. Documentation-only changes.

API Changes

None.

Behavioral Changes

None.

Required skia PR

None.

PR Checklist

• Has tests (N/A - documentation only)
• Rebased on top of main at time of PR
• Merged related skia PRs (N/A)
• Changes adhere to coding standard
• Updated documentation

Original prompt

Can you go through all these docs in the .github, design, and AGENTS.md and make sure they are accurate to the code. It is essential that they represent the code and not try make the code match the docs.

Please check every statement.

Validate assumptions.

The project reputation depends on the docs being accurate.

If you have questions, doubts or concerns. Validate against the code.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.