Initial Arka plugin registry: Official plugins mirror + Arka-signed index

11 plugins from github.com/librefang/librefang-registry plugins/.
index.json / index.json.sig are signed with Arka's Ed25519 key
(not upstream stats.librefang.ai). Private key is not in this repo.

plugins/sentiment-tracker/hooks/README.md

@@ -0,0 +1,14 @@
+# sentiment-tracker hooks
+
+Python hook scripts for the sentiment-tracker plugin. Each script reads a JSON request from stdin and writes a JSON response to stdout.
+
+## Scripts
+
+| Script | Hook | Description |
+|--------|------|-------------|
+| `ingest.py` | ingest | Receives `{"message": "..."}`, analyzes sentiment, returns emotional context as a memory fragment |
+
+## Protocol
+
+- **Input**: JSON object on stdin (fields vary by hook type)
+- **Output**: JSON object on stdout (`ingest_result` with memories, empty for neutral sentiment)