fix(mcp): rename @webclaw/mcp bin to avoid npx PATH shadowing

The published bin was named `webclaw-mcp`, which npx shadows with any existing
`webclaw-mcp` on PATH (Homebrew/cargo/create-webclaw) — so `npx @webclaw/mcp`
silently ran a stale binary instead of the launcher, for exactly our existing
CLI users. Rename the bin to the unique `webclaw-mcp-launcher`; `npx
@webclaw/mcp` still resolves the single bin. Verified end-to-end: with a stale
webclaw-mcp on PATH, npx now runs the launcher and returns 14 tools.

- bin: webclaw-mcp -> webclaw-mcp-launcher; version 0.6.15 -> 0.6.16
- mark webclaw-mcp.mjs executable
- release.yml: version the launcher INDEPENDENTLY of the core release (a
  launcher-only fix must ship without a core bump) — publish the next patch
  above the current npm version and pin RELEASE_TAG to the release tag
- server.json: sync to 0.6.16

Published + deprecated 0.6.15 (bin collision); 0.6.16 is the first good release.

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

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": "0.6.15",
+  "version": "0.6.16",
   "packages": [
     {
       "registryType": "npm",
       "identifier": "@webclaw/mcp",
-      "version": "0.6.15",
+      "version": "0.6.16",
       "transport": {
         "type": "stdio"
       }