Put back the Linux runner and .clangd formatting

Swept into the previous commit by a git add -A while a formatter had run over
them in the background. Unrelated to that commit's subject, and the C++ change
flipped pointer style away from what the Flutter template ships, so it would
come back on every regenerate and churn again.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.clangd

@@ -20,8 +20,8 @@
 # If you do want real analysis of this directory, do it on Linux with the GTK
 # headers present and a compile_commands.json — not by editing the runner.
 If:
-  PathMatch: [.*linux/.*, linux/.*]
+  PathMatch: linux/.*
 
 Diagnostics:
-  Suppress: ["*"]
+  Suppress: '*'
   UnusedIncludes: None