fix: feat(20b): dev-agent reads formula from .profile repo (#85)

lib/formula-session.sh

@@ -155,7 +155,8 @@ load_formula_or_profile() {
   if [ -n "$AGENT_IDENTITY" ] && ensure_profile_repo "$AGENT_IDENTITY"; then
     if [ -f "$PROFILE_FORMULA_PATH" ]; then
       log "formula source: .profile (${PROFILE_FORMULA_PATH})"
-      FORMULA_CONTENT=$(cat "$PROFILE_FORMULA_PATH")
+      # shellcheck disable=SC2034
+      FORMULA_CONTENT="$(cat "$PROFILE_FORMULA_PATH")"
       FORMULA_SOURCE=".profile"
       return 0
     else
@@ -167,7 +168,8 @@ load_formula_or_profile() {
   if [ -n "$fallback_formula" ]; then
     if [ -f "$fallback_formula" ]; then
       log "formula source: formulas/ (fallback) — ${fallback_formula}"
-      FORMULA_CONTENT=$(cat "$fallback_formula")
+      # shellcheck disable=SC2034
+      FORMULA_CONTENT="$(cat "$fallback_formula")"
       FORMULA_SOURCE="formulas/"
       return 0
     else
@@ -176,6 +178,19 @@ load_formula_or_profile() {
     fi
   fi
 
+  # No fallback specified but role provided — construct fallback path
+  if [ -n "$role" ]; then
+    fallback_formula="${FACTORY_ROOT}/formulas/${role}.toml"
+    if [ -f "$fallback_formula" ]; then
+      log "formula source: formulas/ (fallback) — ${fallback_formula}"
+      # shellcheck disable=SC2034
+      FORMULA_CONTENT="$(cat "$fallback_formula")"
+      # shellcheck disable=SC2034
+      FORMULA_SOURCE="formulas/"
+      return 0
+    fi
+  fi
+
   # No fallback specified
   log "ERROR: formula not found in .profile and no fallback specified"
   return 1