feat: align MCP retrieval contract with ra-h

- add external retrieval and confirmation-gated writeback tools across MCP surfaces
- port direct-search-first retrieval support and supporting ranking/query updates
- update MCP docs and skills to treat agent memory files as optional reinforcement

Generated with Claude Code

apps/mcp-server-standalone/README.md

@@ -41,17 +41,35 @@ Restart Claude. Done.
 ## What to Expect
 
 Once connected, Claude will:
-- **Call `getContext` first** to orient itself (stats, contexts, anchors/hubs, skills)
+- **Use `queryNodes` for explicit node lookup** when the user is trying to find a specific existing thing
+- **Use `retrieveQueryContext` when graph context is helpful** for a broader task, question, or request
+- **Use `getContext` only for orientation** when high-level graph state would actually help
 - **Proactively capture knowledge** — when a new insight, decision, person, or reference surfaces, it proposes a specific node (title, description, optional context) so you can approve with minimal friction
 - **Read skills for complex tasks** — skills are editable and shared across internal + external agents
 - **Search before creating** to avoid duplicates
 
+## Recommended Agent Memory Line
+
+If you use external agents through this MCP server, add one short instruction line to your agent memory file (`AGENTS.md`, `CLAUDE.md`, etc.):
+
+```md
+Retrieve relevant context from RA-H before substantive work, and only suggest writing durable context back when it is clearly valuable and the user can confirm yes.
+```
+
+Keep the writeback prompt brief. A good pattern is:
+
+```md
+Add "X" as a node?
+```
+
 ## Available Tools
 
 | Tool | Description |
 |------|-------------|
 | `getContext` | Get graph overview — stats, contexts, recent activity |
+| `retrieveQueryContext` | Pull relevant graph context for a broader current-turn task |
 | `createNode` | Create a new node |
+| `writeContext` | Save one confirmed durable context node after explicit user approval |
 | `queryNodes` | Search nodes by keyword |
 | `queryContexts` | List or inspect contexts |
 | `getNodesById` | Load nodes by ID (includes chunk + metadata) |
@@ -87,6 +105,13 @@ Rules:
 - use `captured_by = "human"` for direct user creation and user-requested agent capture
 - reserve `captured_by = "agent"` for autonomous/background creation only
 
+## Writeback Rule
+
+- Do not ask to save every moderately useful point from the conversation.
+- Only suggest a save when the context is unusually durable and valuable.
+- Keep the ask terse and concrete, for example: `Add "X" as a node?`
+- Never call `writeContext` unless the user has explicitly said yes.
+
 ## Skills
 
 Skills are detailed instruction sets that teach agents how to work with your knowledge base. The default seeded skills are editable and shared by internal + external agents.