fix: plugin no longer vanishes after Claude Code updates

Root cause: plugin registered as directory source in known_marketplaces.json,
which gets wiped on CLI updates. Now registers in extraKnownMarketplaces
(settings.json) as a GitHub source — same mechanism caveman/context-mode use.

Binaries install to ~/.claude-mnemonic/bin/ instead of the Claude-managed
plugins directory. Thin wrapper scripts in the repo let the marketplace
clone find them. Nothing gets cleaned up when Claude refreshes its cache.

Also fixed along the way:
- ONNX Runtime 1.24.3 → 1.26.0 (API v25 mismatch broke all embedding tests)
- Vector client leaked on DB reinit, processQueue had a race on sessionManager
- reloadConfig called os.Exit(0) bypassing graceful shutdown
- Removed dead QueryRowWithTimeout that leaked contexts
- Added tests for graph/watcher/maintenance/update (all were at 0%)

marketplace.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://anthropic.com/claude-code/marketplace.schema.json",
   "name": "claude-mnemonic",
-  "version": "1.0.0",
+  "version": "v0.11.57-dirty",
   "description": "Persistent memory system for Claude Code - stores observations, session summaries, and user prompts with semantic search",
   "owner": {
     "name": "lukaszraczylo",
@@ -12,7 +12,7 @@
   "plugins": [
     {
       "name": "claude-mnemonic",
-      "description": "Persistent memory system for Claude Code - Go implementation with SQLite and ChromaDB vector search",
+      "description": "Persistent memory system for Claude Code - Go implementation with SQLite and sqlite-vec vector search",
       "version": "0.11.105",
       "author": {
         "name": "lukaszraczylo",