M0: toolchain, monorepo scaffold, gateway plugin skeleton, CMP app

- gateway-plugin/: android platform plugin (plugin.yaml + adapter.py
  register(ctx) + no-op AndroidAdapter) + stub modules for M1-M5
- app/: Compose Multiplatform project (shared KMP + androidApp +
  desktopApp) with Gradle wrapper; builds :androidApp:assembleDebug
  and :desktopApp:compileKotlin
- scripts/guard_hermes_agent.sh + pre-commit hook: fail if hermes-agent/
  is staged (read-only reference, never committed)
- .gitignore excludes hermes-agent/; docs/ reference library

gateway-plugin/search.py

@@ -0,0 +1,8 @@
+"""FTS5 session search bridge.
+
+Bridges the ``search {query, scope, chat_id?, thread_id?}`` frame to the
+hermes session store (SQLite + FTS5, ``hermes_state_search.py``) and returns
+``search.results``. Scope: "all" (everywhere) or "chat" (this chat/channel).
+
+Milestone M3.
+"""