chore: modernize CI and update Go toolchain

- Bump Go from 1.19 to 1.26 and update all dependencies
- Rewrite CI workflow with matrix strategy (Linux, macOS, Windows)
- Update GitHub Actions to current versions (checkout@v4, setup-go@v5)
- Update CodeQL actions from v1 to v3
- Fix cross-platform bug in mock/path.go (path.Join -> filepath.Join)
- Clean up dependabot config (weekly schedule, remove stale ignore)

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

vendor/github.com/alecthomas/chroma/v2/lexers/embedded/objectpascal.xml

@@ -31,12 +31,9 @@
       <rule pattern="\{[$].*?\}|\{[-](NOD|EXT|OBJ).*?\}|\([*][$].*?[*]\)">
         <token type="CommentPreproc" />
       </rule>
-      <!-- Comment Single -->
-      <rule pattern="(//.*?)(\n)">
-        <bygroups>
-          <token type="CommentSingle" />
-          <token type="TextWhitespace" />
-        </bygroups>
+      <!-- Comment -->
+      <rule pattern="//.*">
+        <token type="CommentSingle" />
       </rule>
       <!-- Comment Multiline Block -->
       <rule pattern="\([*](.|\n)*?[*]\)">