Surface Clay layout errors on RenderResult

[cowboyd]

Motivation

Clay reports errors during layout (duplicate IDs, capacity exceeded, unbalanced open/close, etc.) via a callback. These were silently discarded, making it impossible for callers to know when their layout had issues.

Approach

• Added errors and error_count fields to the Clayterm struct (no global state)
• The clay_error callback receives the Clayterm instance via Clay's userData pointer and appends errors to the per-instance buffer
• Errors are cleared at the start of each reduce() call, so each render returns only its own errors
• Exposed error_count, error_type, error_message_length, error_message_ptr as WASM exports
• Wired through term-native.ts to term.ts, adding errors: ClayError[] to RenderResult
• Updated renderer spec section 12.3 with the new field and all Clay error types
• Added C code convention to AGENTS.md: no global mutable state

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/clayterm@23

commit: 994adca