release: v4.0.0 — ecosystem integration (marketplace, interop, skill API)

- Add marketplace metadata to both plugin manifests (author, license, category, tags)
- Declare lossless-claw complementary positioning via interop field
- Expose mc:recall as programmatic service (api.exposeService)
- Fix CJK hashtag regex to support Unicode property escapes
- Create MARKETPLACE.md for marketplace listing
- Update README with marketplace install, interop docs, and API docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -1,6 +1,6 @@
 # memory-continuity
 
-**Current release:** `v3.0.0`
+**Current release:** `v4.0.0`
 
 OpenClaw **lifecycle plugin** for short-term working continuity. Preserves structured in-flight work state across `/new`, reset, gateway restarts, model fallback, and context compaction.
 
@@ -46,6 +46,37 @@ Because state injection happens at the hook level (before the model sees anythin
 
 ## Quick Start
 
+### Marketplace Install (recommended)
+
+```bash
+openclaw plugins install https://github.com/dtzp555-max/memory-continuity
+```
+
+### Works with lossless-claw
+
+This plugin does **not** use the `contextEngine` slot. It runs via lifecycle hooks only, so it coexists perfectly with lossless-claw or any other context engine:
+
+- **lossless-claw** = lossless context compression (contextEngine slot)
+- **memory-continuity** = working-state recovery (hooks only)
+
+Install both for the best experience.
+
+### Programmatic API
+
+Other plugins can call MC's recall function programmatically:
+
+```javascript
+// In another plugin's register() function:
+const recall = api.getService("mc:recall");
+if (recall) {
+  const result = await recall.handler(
+    { topic: "deployment issues", maxItems: 3 },
+    ctx
+  );
+  // result.results = [{ date, type, score, summary }, ...]
+}
+```
+
 ### Install
 
 ```bash