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/solidity.xml

@@ -157,8 +157,20 @@
       <rule pattern="(continue|returns|storage|memory|delete|return|throw|break|catch|while|else|from|new|try|for|if|is|as|do|in|_)\b">
         <token type="Keyword"/>
       </rule>
-      <rule pattern="assembly\b">
-        <token type="Keyword"/>
+      <rule pattern="(assembly)(\s+\()(.+)(\)\s+{)">
+        <bygroups>
+          <token type="Keyword"/>
+          <token type="Text"/>
+          <token type="LiteralString"/>
+          <token type="Text"/>
+        </bygroups>
+        <push state="assembly"/>
+      </rule>
+      <rule pattern="(assembly)(\s+{)">
+        <bygroups>
+          <token type="Keyword"/>
+          <token type="Text"/>
+        </bygroups>
         <push state="assembly"/>
       </rule>
       <rule pattern="(contract|interface|enum|event|struct)(\s+)([a-zA-Z_]\w*)">
@@ -235,7 +247,7 @@
         <token type="Punctuation"/>
         <pop depth="1"/>
       </rule>
-      <rule pattern="[(),]">
+      <rule pattern="[(),.]">
         <token type="Punctuation"/>
       </rule>
       <rule pattern=":=|=:">
@@ -276,4 +288,4 @@
       </rule>
     </state>
   </rules>
-</lexer>
+</lexer>