feat: include CHANGELOG.md in npm package and add docs changelog page

.changeset/include-changelog-in-package.md

@@ -0,0 +1,5 @@
+---
+"chanfana": patch
+---
+
+Include CHANGELOG.md in the npm package so AI agents and tools can read the project's change history. Also add a changelog page to the documentation site.

docs/.vitepress/config.mts

@@ -51,6 +51,7 @@ export default defineConfig({
           {text: "Advanced Patterns", link: "/advanced-topics-patterns"},
           {text: "Troubleshooting And FAQ", link: "/troubleshooting-and-faq"},
           {text: "Migration to Chanfana v3", link: "/migration-to-chanfana-3"},
+          {text: "Changelog", link: "/changelog"},
         ],
       },
     ],

docs/changelog.md

@@ -0,0 +1,10 @@
+---
+title: Changelog
+description: A complete history of changes, fixes, and new features in chanfana.
+---
+
+# Changelog
+
+All notable changes to chanfana are documented here.
+
+<!--@include: ../CHANGELOG.md-->

package.json

@@ -28,7 +28,8 @@
     "AGENTS.md",
     "llms.txt",
     "LICENSE",
-    "README.md"
+    "README.md",
+    "CHANGELOG.md"
   ],
   "scripts": {
     "build": "rm -rf dist/ && tsc && tsup src/index.ts src/cli.ts --format cjs,esm --dts --config tsconfig.json --external Hono",