fix: mosaic sync — auto-stash dirty worktree before pull --rebase

git pull --rebase fails with 'cannot pull with rebase: You have
unstaged changes' when the skills repo has local modifications.

Fix: detect dirty index/worktree, stash before pull, restore after.
Also gracefully handle pull failures (warn and continue with existing
checkout) and stash pop conflicts.

packages/mosaic/framework/tools/_scripts/mosaic-sync-skills

@@ -55,7 +55,26 @@ mkdir -p "$MOSAIC_HOME" "$MOSAIC_SKILLS_DIR" "$MOSAIC_LOCAL_SKILLS_DIR"
 if [[ $fetch -eq 1 ]]; then
   if [[ -d "$SKILLS_REPO_DIR/.git" ]]; then
     echo "[mosaic-skills] Updating skills source: $SKILLS_REPO_DIR"
-    git -C "$SKILLS_REPO_DIR" pull --rebase
+
+    # Stash any local changes (dirty index or worktree) before pulling
+    local_changes=0
+    if ! git -C "$SKILLS_REPO_DIR" diff --quiet 2>/dev/null || \
+       ! git -C "$SKILLS_REPO_DIR" diff --cached --quiet 2>/dev/null; then
+      local_changes=1
+      echo "[mosaic-skills] Stashing local changes..."
+      git -C "$SKILLS_REPO_DIR" stash push -q -m "mosaic-sync-skills auto-stash"
+    fi
+
+    if ! git -C "$SKILLS_REPO_DIR" pull --rebase; then
+      echo "[mosaic-skills] WARN: pull failed — continuing with existing checkout" >&2
+    fi
+
+    # Restore stashed changes
+    if [[ $local_changes -eq 1 ]]; then
+      echo "[mosaic-skills] Restoring local changes..."
+      git -C "$SKILLS_REPO_DIR" stash pop -q 2>/dev/null || \
+        echo "[mosaic-skills] WARN: stash pop had conflicts — check $SKILLS_REPO_DIR" >&2
+    fi
   else
     echo "[mosaic-skills] Cloning skills source to: $SKILLS_REPO_DIR"
     mkdir -p "$(dirname "$SKILLS_REPO_DIR")"