feat(mcp): add @webclaw/mcp zero-install launcher as the canonical MCP command

`npx -y @webclaw/mcp` downloads the prebuilt webclaw-mcp binary (verified
against the release SHA256SUMS), caches it, and runs it as an MCP stdio server.
This makes webclaw introspectable in MCP registries (Glama/Smithery/MCP
registry) and installable in any MCP client with no Rust build.

- packages/webclaw-mcp: zero-dep launcher (.mjs) + package.json + README
- README/CLAUDE/examples/smithery: mcpServers config -> npx -y @webclaw/mcp
- registry: point the MCP-registry entry (server.json) at @webclaw/mcp, the
  real stdio server, instead of create-webclaw (a scaffolder); drop
  create-webclaw's mcpName claim so ownership isn't duplicated
- CHANGELOG: unreleased entry

create-webclaw stays as the auto-detect installer. .mcp.json is intentionally
left pointing at the local install path until @webclaw/mcp is published to npm.

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

packages/create-webclaw/package.json

@@ -1,7 +1,6 @@
 {
   "name": "create-webclaw",
   "version": "0.1.6",
-  "mcpName": "io.github.0xMassi/webclaw",
   "description": "Set up webclaw MCP server for AI agents (Claude, Cursor, Windsurf, OpenCode, Codex, Antigravity)",
   "bin": {
     "create-webclaw": "./index.mjs"

packages/create-webclaw/server.json

@@ -3,12 +3,12 @@
   "name": "io.github.0xMassi/webclaw",
   "title": "webclaw",
   "description": "Turn any URL into clean markdown/JSON for AI agents. Self-hostable Firecrawl alternative.",
-  "version": "0.1.6",
+  "version": "0.1.0",
   "packages": [
     {
       "registryType": "npm",
-      "identifier": "create-webclaw",
-      "version": "0.1.6",
+      "identifier": "@webclaw/mcp",
+      "version": "0.1.0",
       "transport": {
         "type": "stdio"
       }