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/episodic-memory/README.md

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+# episodic-memory
+
+Episode-based conversation segmentation and cross-session recall. Automatically detects topic shifts to split conversations into discrete episodes, then recalls relevant past episodes when similar topics arise.
+
+## How it works
+
+**After each turn**, the plugin tracks a "current episode" with accumulated keywords. When the Jaccard similarity between the current turn's keywords and the running episode keywords drops below 0.1 (and the episode has at least 4 messages), it marks the episode as completed with a summary and starts a new one.
+
+**On ingest**, the plugin scores all completed episodes against the incoming message keywords and returns the top 2 matches (overlap > 0.2) as contextual memories including the episode timestamp and summary.
+
+This gives agents episodic recall -- "last time we discussed Docker deployment, we configured nginx as a reverse proxy."
+
+## Hooks
+
+| Hook | Script | Description |
+|------|--------|-------------|
+| ingest | `hooks/ingest.py` | Scores completed episodes against message keywords, returns top matches |
+| after_turn | `hooks/after_turn.py` | Tracks current episode, detects topic shifts, segments conversations |
+
+## Storage
+
+Episodes are stored at `~/.librefang/plugins/episodic-memory/{agent_id}.json`. Max 30 completed episodes per agent (oldest evicted when full).
+
+## Usage
+
+Installed automatically when enabled in agent configuration.