feat: a share link that can't be decrypted says why in a popup

Where its offer was, instead of the footer: the first line of the
reason, r for the whole message (Key Vault's refusals list what to
check), g to go to the key's secret at the link's version, and x to
dismiss.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/ui/app/sharefiles_test.go

@@ -1,6 +1,8 @@
 package app
 
 import (
+	"context"
+	"errors"
 	"net/url"
 	"os"
 	"os/exec"
@@ -312,3 +314,42 @@ func TestPlainEnvNotPickableFromFavourites(t *testing.T) {
 	}
 	t.Fatalf("the starred key isn't among the favourites: %d", len(favs))
 }
+
+// refusing is a provider whose values can't be read, like a disabled
+// version in Key Vault.
+type refusing struct{ provider.Provider }
+
+func (refusing) Value(context.Context, provider.Object) (provider.SecretValue, error) {
+	return provider.SecretValue{}, &provider.Denied{
+		Err:    errors.New("Operation get is not allowed on a disabled secret."),
+		Checks: []string{"the secret's version is enabled"},
+	}
+}
+
+func TestOpenFailsInAPopup(t *testing.T) {
+	key, _ := share.ParseKey("https://" + kv + "/secrets/db-password")
+	link, err := share.Seal(share.Header{Key: key, Repo: "git.example.com/team/app"},
+		[]byte("correct-horse-battery-staple"), []share.File{{Path: ".env", Data: []byte("A=1\n")}}, demoRules)
+	if err != nil {
+		t.Fatal(err)
+	}
+	d := newDriverOpts(t, Options{}, refusing{fake.Azure(0)})
+	d.wait = scryptWait
+	d.send(tea.PasteMsg{Content: link.String()})
+	d.keys("o")
+	p := d.m.prompt
+	if p == nil || p.title != "Can't decrypt the shared files" || !strings.Contains(d.screen(), "Can't use db-password: Operation get is not allowed") {
+		t.Fatalf("not in a popup:\n%s", d.screen())
+	}
+	if strings.Contains(d.screen(), "version is enabled") {
+		t.Error("the whole message is shown before asking")
+	}
+	d.keys("r")
+	if !strings.Contains(d.screen(), "version is enabled") {
+		t.Errorf("r doesn't show the whole message:\n%s", d.screen())
+	}
+	d.keys("g")
+	if _, _, sel := d.selected(); d.m.prompt != nil || (sel != "db-password" && (d.m.nav == nil || d.m.nav.ref.Name != "db-password")) {
+		t.Errorf("g doesn't go to the key: %q, %q\n%s", sel, d.m.flash.text, d.screen())
+	}
+}