feat(rover): show current pipeline step next to Calculate spinner

Compute.run now accepts a `progress` callback and reports human-readable
labels before each pipeline step (loading grid, looking up elevation,
checking road access, scoring cells, etc.). RoverLive feeds it via
send/2 to itself and renders the latest label as small text to the left
of the Calculate button while it's running.

lib/microwaveprop/rover/compute.ex

@@ -90,6 +90,7 @@ defmodule Microwaveprop.Rover.Compute do
       Keyword.get(deps, :buildings_clutter_lookup, &default_building_clutter/1)
 
     hilltop_snap = Keyword.get(deps, :hilltop_snap, &Hilltop.snap/1)
+    progress = Keyword.get(deps, :progress, fn _ -> :ok end)
 
     %{
       home: home,
@@ -105,6 +106,7 @@ defmodule Microwaveprop.Rover.Compute do
     radius_km = max_distance_km * 1.0
     bbox = bbox_around(home, radius_km)
 
+    progress.("Loading propagation grid")
     raw_cells = time_step("scores_at", fn -> scores_at.(band_mhz, valid_time, bbox) end)
 
     in_radius =
@@ -117,17 +119,26 @@ defmodule Microwaveprop.Rover.Compute do
     )
 
     points = Enum.map(in_radius, &{&1.lat, &1.lon})
+    progress.("Looking up elevation")
     elev_map = time_step("elev_lookup", fn -> elev_lookup.(points) end)
+    progress.("Loading building footprints")
     _ = time_step("buildings_load", fn -> BuildingsLoader.ensure_loaded_for_bbox(bbox) end)
+    progress.("Computing path clearance")
     clearance_map = time_step("clearance", fn -> clearance_lookup.(in_radius, selected_stations) end)
+    progress.("Measuring terrain prominence")
     prominence_map = time_step("prominence", fn -> prominence_lookup.(in_radius) end)
 
     road_map =
-      if Application.get_env(:microwaveprop, :rover_road_proximity_enabled, true),
-        do: time_step("road_proximity", fn -> fetch_road_map(road_lookup, in_radius, bbox) end),
-        else: %{}
+      if Application.get_env(:microwaveprop, :rover_road_proximity_enabled, true) do
+        progress.("Checking road access")
+        time_step("road_proximity", fn -> fetch_road_map(road_lookup, in_radius, bbox) end)
+      else
+        %{}
+      end
 
+    progress.("Scanning building clutter")
     clutter_map = time_step("building_clutter", fn -> buildings_clutter_lookup.(in_radius) end)
+    progress.("Scoring cells")
 
     home_elev = home.elev_m || 0
 

lib/microwaveprop_web/live/rover_live.ex

@@ -66,6 +66,7 @@ defmodule MicrowavepropWeb.RoverLive do
        station_form_error: nil,
        home_form_error: nil,
        scoring_loading: false,
+       scoring_step: nil,
        url_loaded?: false
      )}
   end
@@ -324,7 +325,12 @@ defmodule MicrowavepropWeb.RoverLive do
 
     {:noreply,
      socket
-     |> assign(top_candidates: cands, selected_candidate: nil, scoring_loading: false)
+     |> assign(
+       top_candidates: cands,
+       selected_candidate: nil,
+       scoring_loading: false,
+       scoring_step: nil
+     )
      |> apply_scoring_warnings(warnings)
      |> push_event("candidate_paths", %{candidate: nil, paths: []})
      |> push_event("rover_results", %{
@@ -338,10 +344,15 @@ defmodule MicrowavepropWeb.RoverLive do
 
     {:noreply,
      socket
-     |> assign(top_candidates: [], scoring_loading: false)
+     |> assign(top_candidates: [], scoring_loading: false, scoring_step: nil)
      |> put_flash(:error, "Calculate failed: #{inspect(reason)}")}
   end
 
+  @impl true
+  def handle_info({:rover_progress, label}, socket) do
+    {:noreply, assign(socket, scoring_step: label)}
+  end
+
   defp apply_scoring_warnings(socket, []), do: clear_flash(socket)
 
   defp apply_scoring_warnings(socket, warnings) do
@@ -693,10 +704,12 @@ defmodule MicrowavepropWeb.RoverLive do
 
   defp start_scoring(socket) do
     args = scoring_args(socket)
+    pid = self()
+    progress = fn label -> send(pid, {:rover_progress, label}) end
 
     socket
-    |> assign(scoring_loading: true)
-    |> start_async(:scoring, fn -> Compute.run(args) end)
+    |> assign(scoring_loading: true, scoring_step: "Starting…")
+    |> start_async(:scoring, fn -> Compute.run(args, progress: progress) end)
   end
 
   defp scoring_args(socket) do
@@ -908,15 +921,23 @@ defmodule MicrowavepropWeb.RoverLive do
             {band_label(@band)} · Forecast +{@forecast_hour}h
           </span>
         </div>
-        <button
-          type="button"
-          phx-click="calculate"
-          class="btn btn-primary btn-sm"
-          disabled={@scoring_loading}
-        >
-          <span :if={@scoring_loading} class="loading loading-spinner loading-xs"></span>
-          {if @scoring_loading, do: "Calculating…", else: "Calculate"}
-        </button>
+        <div class="flex items-center gap-3">
+          <span
+            :if={@scoring_loading and @scoring_step}
+            class="text-xs text-base-content/60 font-mono"
+          >
+            {@scoring_step}
+          </span>
+          <button
+            type="button"
+            phx-click="calculate"
+            class="btn btn-primary btn-sm"
+            disabled={@scoring_loading}
+          >
+            <span :if={@scoring_loading} class="loading loading-spinner loading-xs"></span>
+            {if @scoring_loading, do: "Calculating…", else: "Calculate"}
+          </button>
+        </div>
       </header>
 
       <div class="flex flex-1 min-h-0">

test/microwaveprop/rover/compute_test.exs

@@ -129,6 +129,38 @@ defmodule Microwaveprop.Rover.ComputeTest do
     assert ref_score - tall_score >= 5.5
   end
 
+  test "calls progress callback with each pipeline step label" do
+    home = %{lat: 33.0, lon: -96.0, elev_m: 200}
+    stations = [%{callsign: "W5LUA", lat: 33.10, lon: -96.625, selected: true}]
+    grid = build_grid(home.lat, home.lon)
+
+    test_pid = self()
+    progress = fn label -> send(test_pid, {:progress, label}) end
+
+    Compute.run(
+      %{
+        home: home,
+        stations: stations,
+        band_mhz: 10_000,
+        valid_time: ~U[2026-04-25 12:00:00Z],
+        mode: :ssb,
+        max_distance_km: 65.0,
+        min_elev_gain: 0
+      },
+      scores_at: fn _, _, _ -> grid end,
+      elev_lookup: fn points -> Map.new(points, fn p -> {p, 250} end) end,
+      clearance_lookup: fn _, _ -> %{} end,
+      prominence_lookup: fn cells -> Map.new(cells, fn c -> {{c.lat, c.lon}, 0} end) end,
+      road_lookup: fn _, _ -> {:error, :stubbed} end,
+      progress: progress
+    )
+
+    assert_received {:progress, "Loading propagation grid"}
+    assert_received {:progress, "Looking up elevation"}
+    assert_received {:progress, "Computing path clearance"}
+    assert_received {:progress, "Scoring cells"}
+  end
+
   test "filters cells failing min_elev_gain" do
     home = %{lat: 33.0, lon: -96.0, elev_m: 500}
     stations = [%{callsign: "W5LUA", lat: 33.1, lon: -96.6, selected: true}]