fix(mosaic): register canonical framework skills

packages/mosaic/framework/framework-manifest.txt

@@ -35,6 +35,8 @@ CONTRIBUTING.md
 defaults/**
 examples/**
 guides/**
+# Shipped framework subtree — canonical skills are upgrade-reconciled.
+skills/**
 install.sh
 install.ps1
 LICENSE
@@ -67,6 +69,9 @@ policy/**
 memory/**
 sources/**
 credentials/**
+# Operator-authored/customized skills live separately from canonical skills/ and
+# must remain structurally unprunable even as skills/** is framework-owned.
+skills-local/**
 # Secret-bearing operator file INSIDE the framework-owned tools/ subtree.
 # Listed explicitly so the deny-wins rule carves it out of tools/**.
 tools/_lib/credentials.json