fix(memory): include type field in output schemas to fix validation error

[aayushbaluni]

Summary

Fixes #3074

When structured output validation is enabled, the memory server's read_graph, search_nodes, and open_nodes tools fail with MCP error -32602 because stored entities contain a type field not declared in the output schema.

Root Cause

Entities in the JSONL knowledge graph include a type property (discriminator for entity vs relation lines), but the tool output schemas used strict validation that rejected unknown properties.

Fix

Declared optional type literals on entity and relation Zod schemas and attach the discriminators when loading from JSONL so structured responses match both the file format and the output schema.

Testing

• Ran memory package Vitest suite (npm test in src/memory)
• Verified TypeScript build succeeds

[olaservo]

Thanks for the PR! The underlying issue with the type discriminator leaking into entity output and tripping additionalProperties: false was fixed in #3213 (commit 8af50b9) by stripping type in loadGraph() instead. Since the field is no longer present on returned entities, declaring it in the schema isn't needed, and we'd prefer the output schema stay strict. Closing as superseded by the merged fix.

Drafted with assistance from Claude Code.