release: rename to unscoped a2amcp, bump 0.1.2

Drops the @a2amcp/mcp scope so the npx invocation collapses to
`npx -y a2amcp` — one token instead of two, no scope to register or
remember.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/cli.ts

@@ -229,7 +229,7 @@ program
       mcpServers: {
         a2a: {
           command: "npx",
-          args: ["-y", "@a2amcp/mcp"],
+          args: ["-y", "a2amcp"],
         },
       },
     };