feat: support manual add and edit for memory facts (#1538)

* feat: support manual add and edit for memory facts

* fix: restore memory updater save helper

* fix: address memory fact review feedback

* fix: remove duplicate memory fact edit action

* docs: simplify memory fact review setup

* docs: relax memory review startup instructions

* fix: clear rebase marker in memory settings page

* fix: address memory fact review and format issues

* fix: address memory fact review feedback

* refactor: make memory fact updates explicit patch semantics

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/docs/MEMORY_SETTINGS_REVIEW.md

@@ -1,34 +1,58 @@
 # Memory Settings Review
 
-Use this when reviewing the Memory Settings search, filter, delete, and clear-all flow locally.
+Use this when reviewing the Memory Settings add/edit flow locally with the fewest possible manual steps.
 
 ## Quick Review
 
-1. Start DeerFlow locally.
+1. Start DeerFlow locally using any working development setup you already use.
+
+   Examples:
 
    ```bash
    make dev
    ```
 
+   or
+
+   ```bash
+   make docker-start
+   ```
+
+   If you already have DeerFlow running locally, you can reuse that existing setup.
+
 2. Load the sample memory fixture.
 
    ```bash
    python scripts/load_memory_sample.py
    ```
 
-3. Open the app and review `Settings > Memory`.
+3. Open `Settings > Memory`.
 
    Default local URLs:
    - App: `http://localhost:2026`
    - Local frontend-only fallback: `http://localhost:3000`
 
-## What To Check
+## Minimal Manual Test
 
-- Search `memory` and confirm multiple facts are matched.
-- Search `Chinese` and confirm text filtering works.
-- Search `workflow` and confirm category text is also searchable.
+1. Click `Add fact`.
+2. Create a new fact with:
+   - Content: `Reviewer-added memory fact`
+   - Category: `testing`
+   - Confidence: `0.88`
+3. Confirm the new fact appears immediately and shows `Manual` as the source.
+4. Edit the sample fact `This sample fact is intended for edit testing.` and change it to:
+   - Content: `This sample fact was edited during manual review.`
+   - Category: `testing`
+   - Confidence: `0.91`
+5. Confirm the edited fact updates immediately.
+6. Refresh the page and confirm both the newly added fact and the edited fact still persist.
+
+## Optional Sanity Checks
+
+- Search `Reviewer-added` and confirm the new fact is matched.
+- Search `workflow` and confirm category text is searchable.
 - Switch between `All`, `Facts`, and `Summaries`.
-- Delete the disposable sample fact and confirm the list updates immediately.
+- Delete the disposable sample fact `Delete fact testing can target this disposable sample entry.` and confirm the list updates immediately.
 - Clear all memory and confirm the page enters the empty state.
 
 ## Fixture Files