chore: exclude tools/, scripts/ from CodeScene analysis

tools/qmd/ contains vendored qmd source code (not our code) that was
dragging the overall code health score down to 6.53.
scripts/ contains one-shot utility scripts, not production code.

Excluding both from CodeScene so the health metric reflects only
the actual app codebase (src/, src-tauri/src/).

.codescenerc

@@ -0,0 +1,9 @@
+{
+  "exclude": [
+    "tools/",
+    "scripts/",
+    "src-tauri/gen/",
+    "coverage/",
+    "dist/"
+  ]
+}