docs: add missing version headers and improve CHANGELOG hierarchy

semantic-release config lacked headerPartial template, causing missing version/date/compare links. Group headers (##) and type headers (###) were at the same level as version headers (##), making hierarchy unclear.

- Added headerPartial for automatic version header generation
- Changed groups (Highlights/Maintenance) to h3, types (Features/Bug Fixes, etc.) to h4
- Manually applied new format to existing CHANGELOG

Author: kubrickcode

.releaserc.js

@@ -1,7 +1,12 @@
-const mainTemplate = `{{#if noteGroups}}
+const headerPartial = `## {{#if linkCompare}}[{{version}}]({{host}}/{{owner}}/{{repository}}/compare/{{previousTag}}...{{currentTag}}){{else}}{{version}}{{/if}} ({{date}})
+`;
+
+const mainTemplate = `{{> header}}
+
+{{#if noteGroups}}
 {{#each noteGroups}}
 
-### {{title}}
+#### {{title}}
 
 {{#each notes}}
 * {{text}}
@@ -10,10 +15,10 @@ const mainTemplate = `{{#if noteGroups}}
 {{/if}}
 
 {{#if highlightGroups}}
-## 🎯 Highlights
+### 🎯 Highlights
 {{~#each highlightGroups}}
 
-### {{title}}
+#### {{title}}
 
 {{#each commits}}
 * {{#if scope}}**{{scope}}:** {{/if}}{{subject}}{{#if hash}} ([{{shortHash}}]({{@root.host}}/{{@root.owner}}/{{@root.repository}}/commit/{{hash}})){{/if}}
@@ -22,10 +27,10 @@ const mainTemplate = `{{#if noteGroups}}
 {{/if}}
 
 {{#if maintenanceGroups}}
-## 🔧 Maintenance
+### 🔧 Maintenance
 {{~#each maintenanceGroups}}
 
-### {{title}}
+#### {{title}}
 
 {{#each commits}}
 * {{#if scope}}**{{scope}}:** {{/if}}{{subject}}{{#if hash}} ([{{shortHash}}]({{@root.host}}/{{@root.owner}}/{{@root.repository}}/commit/{{hash}})){{/if}}
@@ -103,6 +108,7 @@ export default {
 
             return context;
           },
+          headerPartial,
           mainTemplate,
         },
       },
@@ -111,6 +117,7 @@ export default {
       "@semantic-release/changelog",
       {
         changelogFile: "CHANGELOG.md",
+        changelogTitle: "# Changelog",
       },
     ],
     "@semantic-release/npm",