chore: add workflows directory and CODEOWNERS

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Fieldnote-Echo

.github/workflow-templates/.gitkeep

@@ -0,0 +1,4 @@
+# All workflow changes require human approval — navi-bot must not self-approve governance
+.github/workflows/ @Fieldnote-Echo
+.github/workflow-templates/ @Fieldnote-Echo
+CODEOWNERS @Fieldnote-Echo