fix(functions): use cp --update=none instead of non-portable -n

GNU cp warns that -n's behavior is non-portable and may change; the
long form is stable and silences the CI warning.

functions/_agents_repo_ensure_symlink.fish

@@ -20,7 +20,7 @@
 #   having no backup at all.
 #
 #   When <link> is an existing real directory, its contents are copied into
-#   <target> without clobbering (cp -n) before the directory is replaced by
+#   <target> without clobbering (cp --update=none) before the directory is replaced by
 #   the link, so adopting a populated live directory never overwrites the
 #   copy already in the vault.
 #
@@ -60,7 +60,7 @@ function _agents_repo_ensure_symlink --argument-names link target
     else if test -d "$link"
         set -l contents (command ls -A "$link" 2>/dev/null)
         if test (count $contents) -gt 0
-            command cp -rn "$link/." "$target/"; or return 1
+            command cp -r --update=none "$link/." "$target/"; or return 1
         end
         rm -rf "$link"; or return 1
     else if test -e "$link"

functions/agents-init.fish

@@ -354,7 +354,7 @@ function agents-init --description 'scaffold AGENTS/ sub-repo with agent spec fi
                     set -l rel (string replace "$root/" "" "$src")
                     set -l contents (command ls -A "$src" 2>/dev/null)
                     if test (count $contents) -gt 0
-                        if not command cp -rn "$src/." "$canonical/"
+                        if not command cp -r --update=none "$src/." "$canonical/"
                             echo "$c_err""Error: could not merge $rel → AGENTS/$tgt$c_reset" >&2
                             return 1
                         end
@@ -437,7 +437,7 @@ function agents-init --description 'scaffold AGENTS/ sub-repo with agent spec fi
             test -d "$devlogs_dir"; or mkdir -p "$devlogs_dir"
             set -l contents (command ls -A "$docs_devlogs" 2>/dev/null)
             if test (count $contents) -gt 0
-                if not command cp -rn "$docs_devlogs/." "$devlogs_dir/"
+                if not command cp -r --update=none "$docs_devlogs/." "$devlogs_dir/"
                     echo "$c_err""Error: could not copy docs/devlogs → AGENTS/devlogs$c_reset" >&2
                     return 1
                 end

functions/agents-vault.fish

@@ -893,7 +893,7 @@ function agents-vault --description 'track curated agent memory in a host-scoped
             if test -n "$stash"
                 test -f "$stash/origin"
                 and command cat "$stash/origin" >>"$entry/origin" 2>/dev/null
-                command cp -rn "$stash/." "$entry/" 2>/dev/null
+                command cp -r --update=none "$stash/." "$entry/" 2>/dev/null
                 rm -rf "$stash"
             end
             printf 'renamed: %s → %s (%s)\n' "$prev_slug" "$slug" (date -I) >>"$entry/origin"