feat(context-engine): add memory prompt helper

docs/.generated/plugin-sdk-api-baseline.sha256

@@ -1,2 +1,2 @@
-8592ce4554f44cd5325f44f86d37b3057548853cc9bc543b0611e5d9000f262e  plugin-sdk-api-baseline.json
-35393eceb6733d966430369c116511bb15a4b83eec93ebfd3b9a3e8f9ee29cec  plugin-sdk-api-baseline.jsonl
+5bee25156a7699938f2a25419ca44e35113cf6fbd6f533052af68712fc992629  plugin-sdk-api-baseline.json
+f80212552c63be134a2ae456ce2cd4f81507c1569b60493b1d5f965dc2969041  plugin-sdk-api-baseline.jsonl

docs/concepts/context-engine.md

@@ -115,6 +115,8 @@ engine is used automatically.
 A plugin can register a context engine using the plugin API:
 
 ```ts
+import { buildMemorySystemPromptAddition } from "openclaw/plugin-sdk/core";
+
 export default function register(api) {
   api.registerContextEngine("my-engine", () => ({
     info: {
@@ -128,12 +130,15 @@ export default function register(api) {
       return { ingested: true };
     },
 
-    async assemble({ sessionId, messages, tokenBudget }) {
+    async assemble({ sessionId, messages, tokenBudget, availableTools, citationsMode }) {
       // Return messages that fit the budget
       return {
         messages: buildContext(messages, tokenBudget),
         estimatedTokens: countTokens(messages),
-        systemPromptAddition: "Use lcm_grep to search history...",
+        systemPromptAddition: buildMemorySystemPromptAddition({
+          availableTools: availableTools ?? new Set(),
+          citationsMode,
+        }),
       };
     },
 
@@ -249,7 +254,10 @@ OpenClaw resolves when it needs a context engine.
   Memory plugins provide search/retrieval; context engines control what the
   model sees. They can work together — a context engine might use memory
   plugin data during assembly. Plugin engines that want the active memory
-  plugin's legacy prompt guidance can pull it explicitly from
+  prompt path should prefer `buildMemorySystemPromptAddition(...)` from
+  `openclaw/plugin-sdk/core`, which converts the active memory prompt sections
+  into a ready-to-prepend `systemPromptAddition`. If an engine needs lower-level
+  control, it can still pull raw lines from
   `openclaw/plugin-sdk/memory-host-core` via
   `buildActiveMemoryPromptSection(...)`.
 - **Session pruning** (trimming old tool results in-memory) still runs