docs: improve AGENTS.md

Author: gustavotoyota

AGENTS.md

@@ -1,4 +1,7 @@
 - Greenfield project is in /new-deepnotes:
     - vue-shadcn and Tailwind for UI.
     - Feature-based folder structure.
-- Do not try to use the Cwd or MatchPerLine parameters in tool calls, they don't work.
+- Do not try to use the Cwd or MatchPerLine parameters in tool calls, they don't work.
+- Run tests via `pnpm test` from the package root (e.g. `cd packages/session && pnpm test`). Do not use `vitest run --workspace` or `pnpm test --run`.
+- Collab wire has two message types: `DOC` (ProseMirror-only, legacy) and `PAGE_DOC` (page-level spatial). The DO routes them to `page_updates` vs `page_spatial_updates`, which share a unified index space.
+- A DeepNotes "page" is an infinite spatial canvas.