fix watch wakeup test (#1791)

This improves the test introduced in #1736 in a few ways:
* Place the system robot's code inline in the `program` field
    * even though the system bot had been using `instant`, the `run` command itself incurs a delay.  So this ensures the system robot is ready to monitor the cell immediately
* System robot uses exclusively `Intangible` commands in its monitoring loop
    * This allows removal of the `instant` command.
    * `Surveil`, which does not appear in any scenario yet, is made `Intangible`.
* Remove the initial `wait 2` in the player robot's solution.

Tested to ensure that this still exercises the problem that #1736 set out to solve, by commenting out this line (causing the scenario to fail).

01ae0e45d7/src/swarm-engine/Swarm/Game/State/Robot.hs (L396)

## Demo

    scripts/play.sh -i data/scenarios/Testing/1598-detect-entity-change.yaml --autoplay --speed 1

data/scenarios/Testing/1598-detect-entity-change.yaml

@@ -50,11 +50,26 @@ robots:
       invisible: true
     dir: [1, 0]
     program: |
-      run "scenarios/Testing/_1598-detect-entity-change/setup.sw"
+      def doUntilCorrect =
+          herenow <- ishere "dial (G)";
+          if herenow {
+              give base "flower";
+          } {
+              loc <- whereami;
+              surveil loc;
+              wait 1000;
+              doUntilCorrect;
+          }
+          end;
+
+      def go =
+          doUntilCorrect;
+          end;
+
+      go;
     inventory:
       - [1, flower]
 solution: |
-  wait 2;
   move;
   move;
   swap "dial (G)";

data/scenarios/Testing/_1598-detect-entity-change/setup.sw

@@ -1,17 +0,0 @@
-def doUntilCorrect =
-    herenow <- ishere "dial (G)";
-    if herenow {
-        give base "flower";
-    } {
-        watch down;
-        wait 1000;
-        doUntilCorrect;
-    }
-    end;
-    
-def go =
-    instant $
-        doUntilCorrect;
-    end;
-
-go;

src/swarm-lang/Swarm/Language/Syntax.hs

@@ -827,9 +827,13 @@ constInfo c = case c of
       , "Any change to entities at the monitored locations will cause the robot to wake up before the `wait` timeout."
       ]
   Surveil ->
-    command 1 short . doc (Set.singleton $ Query $ Sensing EntitySensing) "Interrupt `wait` upon (remote) location changes." $
-      [ "Like `watch`, but with no restriction on distance."
-      ]
+    command 1 Intangible $
+      doc
+        (Set.singleton $ Query $ Sensing EntitySensing)
+        "Interrupt `wait` upon (remote) location changes."
+        [ "Like `watch`, but instantaneous and with no restriction on distance."
+        , "Supply absolute coordinates."
+        ]
   Heading -> command 0 Intangible $ shortDoc (Set.singleton $ Query $ Sensing RobotSensing) "Get the current heading."
   Blocked -> command 0 Intangible $ shortDoc (Set.singleton $ Query $ Sensing EntitySensing) "See if the robot can move forward."
   Scan ->