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/odin.xml

@@ -51,6 +51,20 @@
         <rule pattern = "\#[a-zA-Z_]+\b">
             <token type = "NameDecorator"/>
         </rule>
+        <rule pattern = "^\#\+\w+\s*$">
+            <token type = "NameAttribute"/>
+        </rule>
+        <rule pattern = "^(\#\+\w+)(\s+)(\!)?([A-Za-z0-9-_!]+)(?:(,)(\!)?([A-Za-z0-9-_!]+))*\s*$">
+            <bygroups>
+                <token type = "NameAttribute"/>
+                <token type = "TextWhitespace"/>
+                <token type = "Operator"/>
+                <token type = "Name"/>
+                <token type = "Punctuation"/>
+                <token type = "Operator"/>
+                <token type = "Name"/>
+            </bygroups>
+        </rule>
         <rule pattern = "\@(\([a-zA-Z_]+\b\s*.*\)|\(?[a-zA-Z_]+\)?)">
             <token type = "NameAttribute"/>
         </rule>