refactor(skills): use .agents/ instead of .agent/ for phased execution

Standardize on the .agents/ directory across all phased-execution
skills (phase state, reports, sessions, validate.sh, PLAN.md, and
per-story/feature/workflow trees). Legacy dot-less agent/ fallbacks
in migration scripts are untouched.

todo-to-phased/scripts/todo-audit.sh

@@ -3,8 +3,8 @@
 #
 # Locates a TODO.md / TODO.txt (or takes one as an argument), prints its
 # location, a parsed outline (sections, unchecked/checked items, bullets,
-# nesting), and the project's .agent/ state, next free phase number
-# (counting .agent/phases/todo/ and complete/ together, zero-padded to 2
+# nesting), and the project's .agents/ state, next free phase number
+# (counting .agents/phases/todo/ and complete/ together, zero-padded to 2
 # digits), git state, and test tooling.
 #
 # Usage:
@@ -140,24 +140,24 @@ else
   printf '%s\n' ${outline[@]+"${outline[@]}"}
 fi
 
-# --- .agent state -----------------------------------------------------------------
+# --- .agents state -----------------------------------------------------------------
 echo
-echo ".agent state:"
+echo ".agents state:"
 a=0
-if [[ -f "$root/.agent/PLAN.md" ]]; then
-  echo "  .agent/PLAN.md: present"
+if [[ -f "$root/.agents/PLAN.md" ]]; then
+  echo "  .agents/PLAN.md: present"
   a=1
 fi
 if [[ -f "$root/AGENTS.md" ]]; then
   echo "  AGENTS.md: present"
   a=1
 fi
-if [[ -f "$root/.agent/validate.sh" ]]; then
-  echo "  .agent/validate.sh: present"
+if [[ -f "$root/.agents/validate.sh" ]]; then
+  echo "  .agents/validate.sh: present"
   a=1
 fi
-todo_dir="$root/.agent/phases/todo"
-complete_dir="$root/.agent/phases/complete"
+todo_dir="$root/.agents/phases/todo"
+complete_dir="$root/.agents/phases/complete"
 list_phases() {
   local dir="$1" entry n t any=0
   for entry in "$dir"/*; do
@@ -176,16 +176,16 @@ list_phases() {
   if (( ! any )); then echo "    (empty)"; fi
 }
 if [[ -d "$todo_dir" ]]; then
-  echo "  .agent/phases/todo:"
+  echo "  .agents/phases/todo:"
   list_phases "$todo_dir"
   a=1
 fi
 if [[ -d "$complete_dir" ]]; then
-  echo "  .agent/phases/complete:"
+  echo "  .agents/phases/complete:"
   list_phases "$complete_dir"
   a=1
 fi
-if (( ! a )); then echo "  (no .agent/ artifacts — Protocol A full conversion needed)"; fi
+if (( ! a )); then echo "  (no .agents/ artifacts — Protocol A full conversion needed)"; fi
 
 max=0
 for d in "$todo_dir" "$complete_dir"; do