Prepare cladm for npm publishing

Add files field, author, repository, and engines to package.json. Add
.npmignore, MIT LICENSE file, GitHub Actions publish workflow on v* tags,
and update README install section with bun install -g / bunx instructions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -7,8 +7,21 @@
   "bin": {
     "cladm": "src/index.ts"
   },
+  "files": [
+    "src/",
+    "README.md",
+    "LICENSE"
+  ],
   "keywords": ["claude", "claude-code", "tui", "terminal", "launcher", "bun"],
   "license": "MIT",
+  "author": "alezmad",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/alezmad/cladm.git"
+  },
+  "engines": {
+    "bun": ">=1.3.0"
+  },
   "devDependencies": {
     "@types/bun": "latest"
   },