feat: add rn watch entity for file change monitoring

lib/completions.sh

@@ -20,7 +20,7 @@ _u7_complete_entities() {
       COMPREPLY=($(compgen -W "text slashes tabs perms owner --help" -- "$cur"))
       ;;
     run|rn)
-      COMPREPLY=($(compgen -W "job script check terminal --help" -- "$cur"))
+      COMPREPLY=($(compgen -W "job script check terminal watch --help" -- "$cur"))
       ;;
   esac
 }
@@ -78,6 +78,7 @@ _u7_complete_args() {
       case "$entity" in
         check) COMPREPLY=($(compgen -W "syntax" -- "$cur")) ; _filedir ;;
         script) _filedir ;;
+        watch) _filedir ;;
       esac
       ;;
   esac

lib/run.sh

@@ -80,6 +80,49 @@ _u7_run() {
       fi
       ;;
 
+    watch)
+      local file="$1"
+      if [[ -z "$file" || "$2" != "run" ]]; then
+        echo "Usage: u7 rn watch <file> run <command>"
+        return 1
+      fi
+      if [[ ! -e "$file" ]]; then
+        echo "File not found: $file"
+        return 1
+      fi
+      shift 2
+      local cmd="$*"
+      if [[ -z "$cmd" ]]; then
+        echo "Usage: u7 rn watch <file> run <command>"
+        return 1
+      fi
+      if [[ "$_U7_DRY_RUN" == "1" ]]; then
+        echo "[dry-run] watch $file and run $cmd on change"
+        return 0
+      fi
+      echo "Watching $file for changes... (Ctrl+C to stop)"
+      if command -v inotifywait &>/dev/null; then
+        while inotifywait -qq -e modify "$file"; do
+          eval "$cmd"
+        done
+      else
+        local last_mod cur_mod
+        last_mod=$(stat -c %Y "$file" 2>/dev/null || stat -f %m "$file" 2>/dev/null)
+        while true; do
+          sleep 1
+          cur_mod=$(stat -c %Y "$file" 2>/dev/null || stat -f %m "$file" 2>/dev/null)
+          if [[ -z "$cur_mod" ]]; then
+            echo "File no longer exists, stopping watch." >&2
+            break
+          fi
+          if [[ "$cur_mod" != "$last_mod" ]]; then
+            last_mod="$cur_mod"
+            eval "$cmd"
+          fi
+        done
+      fi
+      ;;
+
     --help|-h)
       cat << 'EOF'
 u7 rn (run) - Execute/Control
@@ -89,6 +132,7 @@ Usage: u7 rn <entity> [arguments]
 Entities:
   job <cmd> in <time>                    Schedule command (5s, 10m, 1h)
   script <path>                          Execute shell script
+  watch <file> run <command>             Watch file and run command on change
   <command> in background                Run command in background
   <command> with priority <nice>         Run with CPU priority
   check syntax in file <path>            Check single file syntax

test.sh

@@ -988,6 +988,30 @@ else
     ((PASSED++))
 fi
 
+# ===== rn watch tests =====
+
+# Test: rn watch usage (missing args)
+result=$(u7 rn watch 2>&1)
+assert_contains "rn watch shows usage on missing args" "Usage" "$result"
+
+# Test: rn watch usage (missing run keyword)
+touch watch_target.txt
+result=$(u7 rn watch watch_target.txt 2>&1)
+assert_contains "rn watch shows usage when run keyword missing" "Usage" "$result"
+
+# Test: rn watch file not found
+result=$(u7 rn watch nonexistent_file.txt run echo hi 2>&1)
+assert_contains "rn watch reports missing file" "not found" "$result"
+
+# Test: rn watch dry-run
+touch watch_target.txt
+result=$(u7 -n rn watch watch_target.txt run echo hello 2>&1)
+assert_equals "rn watch dry-run output" "[dry-run] watch watch_target.txt and run echo hello on change" "$result"
+
+# Test: rn watch help text includes watch
+result=$(u7 rn --help 2>&1)
+assert_contains "rn help mentions watch" "watch" "$result"
+
 # ===== sh log tests =====
 
 # Setup: create a temp log file