chore(mcp): align @webclaw/mcp npm README, lockstep version, add CI publish

- README: rewrite to match the main webclaw README's voice/positioning
  (clean markdown/JSON/LLM-ready context + anti-bot angle), accurate 14-tool
  local/cloud split, consistent links. This is the package's npm landing page.
- version @webclaw/mcp in lockstep with the core release (0.6.15) so
  @webclaw/mcp@X.Y.Z always installs webclaw vX.Y.Z; sync the MCP-registry
  server.json version to match.
- release.yml: add an `npm` job (needs: release) that pins the launcher's
  RELEASE_TAG to the tag and publishes @webclaw/mcp on stable tags. Requires
  an NPM_TOKEN repo secret with publish rights on the @webclaw scope.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/webclaw-mcp/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@webclaw/mcp",
-  "version": "0.1.0",
+  "version": "0.6.15",
   "description": "Zero-install launcher for the webclaw MCP server: web extraction and anti-bot access for AI agents. Runs `npx @webclaw/mcp`.",
   "type": "module",
   "bin": {