fix(.agents): list all 5 skills in manifest.yaml enabled.skills

sf-wiki, forge-autonomous-runtime, forge-command-surface, nix-build,
and smoke-test are all present in .agents/skills/ and must be declared
in enabled.skills per the AGENTS-1 spec.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.agents/manifest.yaml

@@ -17,7 +17,12 @@ enabled:
   policies:
     - default-safe
     - yolo
-  skills: []
+  skills:
+    - forge-autonomous-runtime
+    - forge-command-surface
+    - nix-build
+    - sf-wiki
+    - smoke-test
 
 resolution:
   enableUserOverlay: false