Updates docs to match the new behavior where metadata-only PATCH updates do not trigger reindexing:
- **update-delete-memories/overview.mdx** — Distinguishes content changes (reindex) vs metadata-only (no reindex), adds a note about `accepted`-style updates
- **document-operations.mdx** — Clarifies that only content changes trigger reprocessing
- **add-memories.mdx** and **add-memories/overview.mdx** — Add notes on metadata-only behavior
- **memory-api/ingesting.mdx** — Splits update behavior into content vs metadata-only
- **memory-api/creation/adding-memories.mdx** — Adds note for the “Adding Additional Metadata to Files” flow
