feat(rover-planning): backfill resets stale :complete paths to repopulate term blob

Existing Path rows persisted before the PathCompute extraction shipped
have no "term" key in their result map, so the live /path page hits
the :stale_term branch and falls back to live recompute when the
operator clicks a row. The hourly backfill cron now flips those
:complete rows back to :pending so the path-profile worker rerolls
them with the new full-output term, after which row clicks render
from cache instantly. The flip uses Postgres's jsonb_exists() so it's
a single targeted UPDATE instead of pulling rows into Elixir.

lib/microwaveprop/rover_planning.ex

@@ -175,17 +175,20 @@ defmodule Microwaveprop.RoverPlanning do
   end
 
   @doc """
-  Walks every mission and re-enqueues any (rover_location × station)
-  pair whose `Path` is missing or not `:complete`. Existing complete
-  rows are left alone — the worker also short-circuits on `:complete`,
-  so this is idempotent and safe to run on a cron.
+  Walks every mission and re-enqueues any (rover_location × station ×
+  band) pair whose `Path` is missing, not `:complete`, OR whose
+  cached `result` lacks the `"term"` blob (paths persisted before
+  PathCompute extraction shipped — the row click on /rover-planning
+  needs that blob to render `/path` from cache instead of recomputing).
 
-  Use case: a rolling deploy or a transient elevation-API failure left
-  some missions with `:pending` / `:failed` entries; the next backfill
-  tick recovers them without operator action.
+  Idempotent: the path-profile worker short-circuits on `:complete`,
+  and we only nudge :complete rows back to :pending when their term
+  is missing. Safe to run on a cron.
   """
   @spec backfill_paths() :: :ok
   def backfill_paths do
+    reset_paths_missing_term()
+
     Mission
     |> Repo.all()
     |> Repo.preload(stations: from(s in Station, order_by: s.position))
@@ -194,6 +197,20 @@ defmodule Microwaveprop.RoverPlanning do
     :ok
   end
 
+  # Flip :complete paths whose result map has no "term" key back to
+  # :pending so the next reconcile pass picks them up. JSONB
+  # `key_exists` is `?` in pg, but Ecto's fragment uses `?` as a
+  # placeholder — use the function form `jsonb_exists/2` instead.
+  defp reset_paths_missing_term do
+    Repo.update_all(
+      from(p in Path,
+        where: p.status == :complete,
+        where: not fragment("jsonb_exists(?, 'term')", p.result)
+      ),
+      set: [status: :pending]
+    )
+  end
+
   defp enqueue_paths_for(%Mission{} = mission) do
     mission
     |> desired_tuples()