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/topic-memory/README.md

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+# topic-memory
+
+Topic-aware memory recall using keyword clustering. Tracks conversation topics per agent and recalls related context when similar topics arise in future conversations.
+
+## How it works
+
+**After each turn**, the plugin extracts keywords from user and assistant messages, then either merges them into an existing topic cluster (Jaccard similarity > 0.3) or creates a new one. Each cluster stores a keyword set, a summary, a hit count, and a last-seen timestamp.
+
+**On ingest**, the plugin scores all stored topic clusters against the incoming message keywords using Jaccard similarity and returns the top 3 matches (threshold > 0.15) as contextual memories.
+
+This gives agents cross-conversation topic awareness -- if a user discussed Python async patterns last week, bringing up `asyncio` today will recall that context.
+
+## Hooks
+
+| Hook | Script | Description |
+|------|--------|-------------|
+| ingest | `hooks/ingest.py` | Scores stored topics against message keywords, returns top matches |
+| after_turn | `hooks/after_turn.py` | Extracts keywords, merges or creates topic clusters |
+
+## Storage
+
+Topic clusters are stored at `~/.librefang/plugins/topic-memory/{agent_id}.json`. Max 50 clusters per agent (lowest hit-count evicted when full).
+
+## Usage
+
+Installed automatically when enabled in agent configuration.