feat: track both entry files in the repo

~/.claude/CLAUDE.md was in no git repo despite heavy editing, and
~/.codex/AGENTS.md was a hand-synced duplicate of it. Both now live in
entry/ and import the shared fragments; RTK.md moves to claude-md/ so
Codex stops carrying its own copy.

Claude's imports are ~/-anchored so they resolve through the symlink.

Also drops kt from the comment rule scope.

nix/home.nix

@@ -23,6 +23,11 @@
 
     # Path-scoped: loads only when Claude reads a matching source file.
     ".claude/rules/code-comments.md".source = "${agent-skills}/claude-md/code-comments.md";
+    ".claude/RTK.md".source = "${agent-skills}/claude-md/RTK.md";
+
+    # Entry files: machine-local sections + @imports of the fragments above.
+    ".claude/CLAUDE.md".source = "${agent-skills}/entry/CLAUDE.md";
+    ".codex/AGENTS.md".source = "${agent-skills}/entry/codex-AGENTS.md";
 
   };
 }