feat(memory): add adapter contract for agent memory

[drewstone]

Summary

• add a provider-neutral memory adapter contract under @tangle-network/agent-knowledge/memory
• add source-record conversion so memory hits can become grounded knowledge evidence
• add a Neo4j Agent Memory bridge without a runtime dependency on @neo4j-labs/agent-memory

Hardening

• typecheck CI against @neo4j-labs/agent-memory@0.4.0 as a dev-only dependency
• support the published TypeScript SDK methods: shortTerm.addMessage/searchMessages/getContext, longTerm.addEntity/addPreference/addFact/searchEntities/searchPreferences, and reasoning.getSimilarTraces
• preserve generic search / getContext and snake_case bridge-style fallbacks
• normalize hosted conversation context reflections, observations, and recent messages into source-grounded memory hits
• preserve SDK unsupported-transport errors instead of masking them with fallback writes

Validation

• pnpm exec biome check --write README.md package.json pnpm-lock.yaml src/memory tests/memory-adapter.test.ts tsup.config.ts
• pnpm typecheck
• pnpm test
• pnpm build
• git diff --check