feat(plugin): holographic memory store adapted to MemoryProvider interface

Adapts PR #2351 by dusterbloom to use the new MemoryProvider ABC.
Core files (store.py, retrieval.py, holographic.py) unchanged from
the original PR. The __init__.py register() function now calls
ctx.register_memory_provider() instead of ctx.register_tool().

HolographicMemoryProvider implements:
- initialize() — creates SQLite DB + FactRetriever
- system_prompt_block() — shows fact count when active
- prefetch(query) — FTS5 search for turn context
- get_tool_schemas() — fact_store (9 actions) + fact_feedback
- handle_tool_call() — routes to store/retriever
- on_session_end() — auto-extract preferences (opt-in)
- on_memory_write() — mirrors builtin memory writes as facts

39 tests (22 HRR math + 17 provider adapter), all passing.

plugins/hermes-memory-store/plugin.yaml

@@ -0,0 +1,6 @@
+name: hermes-memory-store
+version: 0.1.0
+description: Structured memory backend with SQLite storage, trust scoring, entity resolution, and hybrid keyword/BM25 retrieval.
+author: peppi
+hooks:
+  - on_session_end