fix: disable Biome in CodeRabbit and remove broken biome.jsonc

The biome.jsonc added in 3edf777 used `files.ignore`, which doesn't
exist in Biome 2.x. Biome 2.x uses negated patterns in `files.includes`
instead, so CodeRabbit's Biome 2.5.1 silently ignored the config.

Since this repo has no standard JS files (only Claude Code skill scripts
with non-standard syntax like top-level returns), disable Biome entirely
in CodeRabbit rather than fixing the config.

Assisted-by: Claude:claude-opus-4-6

Author: cblecker

.coderabbit.yaml

@@ -1,3 +1,7 @@
+# yaml-language-server: $schema=https://coderabbit.ai/integrations/schema.v2.json
 reviews:
   path_filters:
     - "!gws/skills/**"  # Vendored upstream gws generate-skills output
+  tools:
+    biome:
+      enabled: false