chore: refresh project agent guidance

Clarify template guidance, move skills, and document formatter and
commit conventions.

Co-authored-by: GPT-6 Luna <gpt.6.luna@openrouter.ai>

.oxfmtrc.json

@@ -0,0 +1,19 @@
+{
+  "ignorePatterns": [
+    "node_modules",
+    "dist",
+    ".git",
+    "tests/microprogs.inc",
+    "ruze/cpu/a64_table.cpp",
+    "ruze/cpu/libc_shims.inc"
+  ],
+  "overrides": [
+    {
+      "files": ["*.md"],
+      "options": {
+        "printWidth": 80,
+        "proseWrap": "always"
+      }
+    }
+  ]
+}