fix(goals): Mark complete confirm warns at sub-100% progress

Behavioural audit edge case. A user clicking "Mark complete" at
80% saw the same generic confirm body as at 105% ("It leaves the
Ongoing list…"). Sunk-cost-fallacy inversion + premature closure:
once labelled complete, the goal anchors success on the truncated
amount; future similar goals get smaller targets (regression to
the lower aspiration).

When `progress_percent < 100`, swap the confirm body to a
specific one — "You're at 80% — $X of $Y. Marking complete records
this as your achievement instead of the original target. Continue,
or close this and adjust the target instead?" Doesn't block the
action (some "stop short" cases are healthy — CFP literature
explicitly endorses changing your mind), but makes the trade-off
visible. Keep the original copy for the ≥ 100% case.

`confirm_complete_body_short` is a new locale key; the kebab-menu
builder picks between it and `confirm_complete_body` per-render.

app/views/goals/show.html.erb

@@ -62,6 +62,14 @@
           <% menu.with_item(variant: "button", text: t(".resume"), icon: "play", href: resume_goal_path(@goal), method: :patch) %>
         <% end %>
         <% if @goal.may_complete? %>
+          <% complete_body = if @goal.progress_percent < 100
+                              t(".confirm_complete_body_short",
+                                progress: @goal.progress_percent,
+                                saved: @goal.current_balance_money.format(precision: 0),
+                                target: @goal.target_amount_money.format(precision: 0))
+                            else
+                              t(".confirm_complete_body")
+                            end %>
           <% menu.with_item(
                variant: "button",
                text: t(".complete"),
@@ -70,7 +78,7 @@
                method: :patch,
                confirm: CustomConfirm.new(
                  title: t(".confirm_complete_title"),
-                 body: t(".confirm_complete_body"),
+                 body: complete_body,
                  btn_text: t(".confirm_complete_cta")
                )
              ) %>

config/locales/views/goals/en.yml

@@ -146,6 +146,7 @@ en:
         adjust_target_cta: Adjust target instead
       confirm_complete_title: Mark this goal complete?
       confirm_complete_body: It leaves the Ongoing list. You can still archive or restore it later.
+      confirm_complete_body_short: "You're at %{progress}% — %{saved} of %{target}. Marking complete records this as your achievement instead of the original target. Continue, or close this and adjust the target instead?"
       confirm_complete_cta: Mark complete
       confirm_archive_title: Archive this goal?
       confirm_archive_body: Archived goals disappear from the main list. You can restore them later.