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/keyword-memory/README.md

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+# keyword-memory
+
+Extracts keywords and named entities from user messages and returns them as contextual memories. Gives agents awareness of conversation topics without requiring external NLP libraries.
+
+## Extraction Techniques
+
+- **Plain keywords**: Splits words, filters English stopwords (~50 words), removes short tokens
+- **Capitalized phrases**: Detects multi-word proper nouns and mid-sentence capitalized words
+- **Emails and URLs**: Regex pattern matching
+- **Numbers with units**: e.g. 500ms, 10GB, 3.5GHz
+- **Dates**: YYYY-MM-DD, MM/DD/YYYY, DD.MM.YYYY formats
+- **Technical terms**: camelCase, snake_case, dotted identifiers (e.g. `os.path`)
+
+Results are deduplicated and capped at 10 keywords.
+
+## Hooks
+
+| Hook | Script | Description |
+|------|--------|-------------|
+| ingest | `hooks/ingest.py` | Extracts keywords from the user message and returns them as a memory fragment |
+
+## Example Output
+
+```json
+{"type": "ingest_result", "memories": [{"content": "[keyword-memory] Key topics: GPT-4, machine_learning, data pipeline, https://example.com"}]}
+```
+
+If no meaningful keywords are found, returns an empty memories list.
+
+## Usage
+
+Installed automatically when enabled in agent configuration. No external dependencies required (stdlib only).