v0.270.0: no update for a current app (R-679); an interrupted install is reported (R-681); a restore brings back the pinned version's health check (R-669); R-674

Five red-proofs. MinAgent 0.131.0 unchanged.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/stacks/r674_head_test.go

@@ -0,0 +1,30 @@
+package stacks
+
+import (
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// R-674 (v0.270.0): a pin equal to the ladder's newest `to` is AT THE HEAD — the log must not call it
+// "older than the ladder".
+//
+// COMPANION RED-PROOF (REPORT.md): drop the head branch in nextLadderStep → "the head was called older
+// than the ladder".
+func TestR674_HeadIsNotCalledOlder(t *testing.T) {
+	dir := t.TempDir()
+	mustWrite(t, filepath.Join(dir, ".felhom.yml"), "display_name: X\nupdate_ladder:\n"+ladderLine(ladderA, ladderB)+ladderLine(ladderB, ladderC))
+	mustWrite(t, filepath.Join(dir, "docker-compose.yml"), "services:\n  web:\n    image: "+ladderC+"\n")
+	step, err := nextLadderStep(dir, map[string]string{"web": ladderC})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(step.Why, "older than the ladder") || !strings.Contains(step.Why, "AT THE HEAD") {
+		t.Fatalf("the head was called older than the ladder: %q", step.Why)
+	}
+	// Control: a pin the ladder does not know is still said so.
+	step, _ = nextLadderStep(dir, map[string]string{"web": "nextcloud:30.0.0-apache"})
+	if !strings.Contains(step.Why, "matches no update_ladder entry") {
+		t.Fatalf("the unknown-pin sentence changed: %q", step.Why)
+	}
+}