feat: extract and load user working memory from skill sync payloads (#357)

* feat: implement user working memory extraction from skill sync payloads

- Added functionality to enable the extraction of user working memory from successful skill syncs, allowing for persistent storage of user preferences, goals, constraints, and entities.
- Introduced a new configuration option in  to toggle working memory extraction.
- Created comprehensive documentation on the working memory extraction process, detailing its implementation and privacy considerations.
- Updated memory loading logic to include working memory entries in the context provided to agents, enhancing personalization capabilities.
- Enhanced logging for memory extraction processes to improve observability and debugging.

This feature enhances the user experience by allowing skills to maintain context across interactions, improving the overall effectiveness of the OpenHuman platform.

* docs: update architecture documentation to include user working memory integration

* refactor: centralize working memory constants and enhance extraction logic

- Moved `WORKING_MEMORY_KEY_PREFIX` and `WORKING_MEMORY_LIMIT` constants to `memory_context.rs` for better organization and accessibility.
- Updated `MemoryLoader` to utilize these constants, improving code clarity.
- Enhanced working memory extraction logic in `MemoryWriteJob` to conditionally persist user working-memory documents based on the job type.
- Improved logging for memory extraction processes to provide clearer insights during execution.
- Adjusted tests to ensure consistent behavior with the new working memory extraction logic.

* chore: update OpenHuman version to 0.51.8 and refactor JSON-RPC test for clarity

- Bumped the OpenHuman version in Cargo.lock from 0.51.6 to 0.51.8.
- Refactored the JSON-RPC end-to-end test to improve readability by encapsulating the result assertion logic within a block, enhancing clarity in the flow of data handling.

.env.example

@@ -140,6 +140,9 @@ SKILLS_REGISTRY_URL=
 # skill discovery and install will copy from this directory instead of downloading.
 # Example: SKILLS_LOCAL_DIR=/Users/you/work/openhuman-skills/skills
 SKILLS_LOCAL_DIR=
+# [optional] Enable sync-derived user working memory extraction (default: true).
+# Set to false to disable persisting `working.user.*` docs from skill sync payloads.
+OPENHUMAN_SKILLS_WORKING_MEMORY_ENABLED=true
 
 # ---------------------------------------------------------------------------
 # Error Reporting (Sentry)