fix(rover-planning): keep only_known_good checked across phx-change events

The hidden 'false' shadow input was rendered after the checkbox, so when
both were submitted the 'false' value overwrote the checkbox 'true' in
the resulting params map. Move the hidden input before the checkbox so
the checked value wins (matching the core_components checkbox pattern).

lib/microwaveprop_web/live/rover_planning_live/form.ex

@@ -217,6 +217,7 @@ defmodule MicrowavepropWeb.RoverPlanningLive.Form do
         </div>
 
         <label class="flex items-center gap-2 cursor-pointer">
+          <input type="hidden" name="mission[only_known_good]" value="false" />
           <input
             type="checkbox"
             name="mission[only_known_good]"
@@ -224,7 +225,6 @@ defmodule MicrowavepropWeb.RoverPlanningLive.Form do
             checked={Phoenix.HTML.Form.normalize_value("checkbox", @form[:only_known_good].value)}
             class="checkbox checkbox-primary"
           />
-          <input type="hidden" name="mission[only_known_good]" value="false" />
           <span>
             Only check against known good locations
             <span class="text-xs opacity-70 block">

test/microwaveprop_web/live/rover_planning_live_test.exs

@@ -83,6 +83,31 @@ defmodule MicrowavepropWeb.RoverPlanningLiveTest do
                live(conn, ~p"/rover-planning/new")
     end
 
+    test "typing into the form does not flip the only_known_good checkbox", %{conn: conn} do
+      user = AccountsFixtures.user_fixture()
+      conn = log_in_user(conn, user)
+      {:ok, lv, _html} = live(conn, ~p"/rover-planning/new")
+
+      html =
+        lv
+        |> form("#mission-form",
+          mission: %{
+            name: "Some name",
+            band_mhz: "10000",
+            rover_height_ft: "8.0",
+            station_height_ft: "30.0",
+            only_known_good: "true",
+            stations: %{"0" => %{input: ""}}
+          }
+        )
+        |> render_change()
+
+      # The default-checked box must STILL be checked after a phx-change.
+      # Hidden "false" + checkbox "true" with hidden first = checkbox wins.
+      assert html =~
+               ~s(name="mission[only_known_good]" value="true" checked)
+    end
+
     test "logged-in user can create a mission with a callsign-input station",
          %{conn: conn} do
       user = AccountsFixtures.user_fixture()