ci: add path filters to skip CI on non-source changes

Adds paths filter to push and pull_request triggers to prevent
unnecessary CI runs when only documentation or config files change.
Workflow now triggers only on src/, build files, gradle/, tools/,
and workflow changes.

Author: GhostTypes

.github/workflows/ci.yml

@@ -6,7 +6,21 @@ on:
     branches:
       - main
       - master
+    paths:
+      - 'src/**'
+      - 'build.gradle*'
+      - 'settings.gradle*'
+      - 'gradle/**'
+      - 'tools/**'
+      - '.github/workflows/**'
   pull_request:
+    paths:
+      - 'src/**'
+      - 'build.gradle*'
+      - 'settings.gradle*'
+      - 'gradle/**'
+      - 'tools/**'
+      - '.github/workflows/**'
 
 permissions:
   contents: read