Fix spelling typos across codebase

[luojiyin1987]

This PR fixes multiple spelling typos found in the codebase.

Code Constants

• Fixed `NOTIFICAITON` → `NOTIFICATION` in:
  • `src/openagents/config/globals.py`
  • `src/openagents/core/network.py`

Documentation

• Fixed typos in:
  • `README.md`: "havn" → "haven"
  • `docs/getting-started/quick-start-guide.mdx`: "Afer" → "After", "importan" → "important", "differen" → "different"
  • `docs/tutorials/demo-grammar-check-forum.mdx`: "utlities" → "utilities", "becuase" → "because"

Changelogs

• Fixed typos in:
  • `changelogs/blogs/2025-11-27-demo-showcase.md`: "becuase" → "because", "carreer" → "career"
  • `changelogs/docs/2025-11-27-demo-showcase.md`: "becuase" → "because", "converstion" → "conversation"
  • `changelogs/docs/2025-12-20-grammar-forum-bedrock.md`: "becuase" → "because", "converstion" → "conversation"

Studio UI Components

• Fixed typos in:
  • `studio/src/components/ui/sheet.tsx` & `studio/src/components/layout/ui/sheet.tsx`: "strech" → "stretch"
  • `studio/src/components/ui/menubar.tsx` & `studio/src/components/layout/ui/menubar.tsx`: "tirgger" → "trigger"

Notes

The following were intentionally NOT changed as they require more careful handling:

• `network_discovey.py` - filename typo (requires file rename)
• `desitnation_id` - attribute name in `event.py` (API breaking change)
• Grammar checker demo files - intentionally contain typos for demonstration purposes

[linear]

OADEV-26