Add optional TOON context formatting

[shaihi]

Summary

• add optional markdown | json | toon rendering for context-bundle rendered output
• thread format through API, client, MCP, memory bridge, and AI SDK helpers without changing JSON transport or MongoDB storage
• add deterministic TOON token benchmark and docs with measured wins/losses
• stabilize two search-readiness polling tests that were flaky in full-suite runs

Validation

• bun run check-types
• bun run test
• bun run benchmark:toon
• focused Vitest coverage for formatter, context bundle, client, API, and MCP

Benchmark note

TOON saved tokens on 4/7 deterministic fixtures and lost tokens on 3/7 versus compact JSON. Docs avoid broad compression claims and recommend measuring representative payloads before enabling TOON.