feat: add Convex RAG tools and calendar tool tests

- Introduced Convex RAG tools including:
  - `convexChunker`: A tool for processing document content and storing chunk embeddings in ConvexVector with configurable chunking strategies and embedding generation.
  - `convexGraphQueryTool`: A graph-based retrieval augmented generation tool using ConvexVector for semantic search.
  - `convexVectorQueryTool`: A similarity search tool for semantic content retrieval and question answering using ConvexVector.
  - `convexRerankerTool`: A tool for reranking initial ConvexVector search results using a semantic reranker with configurable weights.

- Implemented input and output schemas for each tool using Zod for validation.
- Added logging and tracing capabilities for better observability during tool execution.
- Created tests for the calendar tool to ensure functionality:
  - Validated default source selection based on platform.
  - Checked explicit source overrides.
  - Parsed events from ICS calendar exports.
  - Loaded events from an ICS file on Linux.
  - Ensured an ICS file is required when falling back to the ICS source on Linux.

Co-authored-by: Copilot <copilot@github.com>