Revert to v2.18.10 - Remove session persistence (v2.19.0-v2.19.5) (#322)

After 5 consecutive hotfix attempts, session persistence has proven
architecturally incompatible with the MCP SDK. Rolling back to last
known stable version.

## Removed
- 16 new files (session types, docs, tests, planning docs)
- 1,100+ lines of session persistence code
- Session restoration hooks and lifecycle events
- Retry policy and warm-start implementations

## Restored
- Stable v2.18.10 codebase
- Library export fields (from PR #310)
- All core MCP functionality

## Breaking Changes
- Session persistence APIs removed
- onSessionNotFound hook removed
- Session lifecycle events removed

This reverts commits fe13091 through 1d34ad8.
Restores commit 4566253 (v2.18.10, PR #310).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

package.runtime.json

@@ -1,17 +1,8 @@
 {
   "name": "n8n-mcp-runtime",
-  "version": "2.19.5",
+  "version": "2.18.10",
   "description": "n8n MCP Server Runtime Dependencies Only",
   "private": true,
-  "main": "dist/index.js",
-  "types": "dist/index.d.ts",
-  "exports": {
-    ".": {
-      "types": "./dist/index.d.ts",
-      "require": "./dist/index.js",
-      "import": "./dist/index.js"
-    }
-  },
   "dependencies": {
     "@modelcontextprotocol/sdk": "^1.13.2",
     "@supabase/supabase-js": "^2.57.4",