agent v0.37.0: re-assert mounted-but-DISABLED units (live felhom-usb fix)

The skip-if-mounted optimization defeated the actual root cause: felhom-usb is
mounted now but its unit is `disabled`, so a host reboot would not auto-mount
it. ReassertEnrolledMounts now skips ONLY the durable steady state (mounted AND
enabled) via the pure shouldReassertMount; a mounted-but-disabled unit is
re-asserted so enable --now re-creates the wants-symlink. Enabled-state read by
privilege-free Lstat of the multi-user.target.wants symlink (unitEnabled) — no
systemctl is-enabled subprocess, no new sudoers entry.

Tests: TestShouldReassertMount (4 combos), TestUnitEnabled (wants-symlink).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/storage/hostops_test.go

@@ -192,3 +192,52 @@ type errExitT int
 
 func (e errExitT) Error() string { return "exit status nonzero" }
 func errExit(code int) error     { return errExitT(code) }
+
+// TestShouldReassertMount pins the host-reboot re-assert decision. The load-bearing case is
+// mounted-but-DISABLED (the live felhom-usb bug): the drive serves now, but with no wants-symlink a
+// host reboot would not auto-mount it, so it MUST still be re-asserted (enable --now re-creates the
+// symlink). Only mounted+enabled is the durable steady state we skip.
+func TestShouldReassertMount(t *testing.T) {
+	cases := []struct {
+		mounted, enabled, want bool
+		name                   string
+	}{
+		{true, true, false, "mounted+enabled → durable, skip"},
+		{true, false, true, "mounted+DISABLED → re-assert (the live bug: reboot would not auto-mount)"},
+		{false, true, true, "unmounted+enabled → re-assert (mount it now)"},
+		{false, false, true, "unmounted+disabled → re-assert (enable + mount)"},
+	}
+	for _, c := range cases {
+		if got := shouldReassertMount(c.mounted, c.enabled); got != c.want {
+			t.Errorf("%s: shouldReassertMount(%v,%v)=%v want %v", c.name, c.mounted, c.enabled, got, c.want)
+		}
+	}
+}
+
+// TestUnitEnabled detects the WantedBy=multi-user.target wants-symlink with a privilege-free Lstat
+// (no systemctl subprocess), so the re-assert can tell a disabled unit from an enabled one.
+func TestUnitEnabled(t *testing.T) {
+	unitDir := t.TempDir()
+	ops := NewSudoHostOps(SudoHostOpsConfig{
+		Runner:   &recordingRunner{},
+		Bins:     Binaries{Systemctl: "/usr/bin/systemctl", Install: "/usr/bin/install"},
+		UnitDir:  unitDir,
+		StageDir: t.TempDir(),
+		Logger:   quietLogger(),
+	})
+	const unit = "mnt-felhom-usb.mount"
+	if ops.unitEnabled(unit) {
+		t.Fatal("a unit with no wants-symlink must report NOT enabled (the felhom-usb disabled state)")
+	}
+	wants := filepath.Join(unitDir, "multi-user.target.wants")
+	if err := os.MkdirAll(wants, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	// systemd points the wants-symlink at the real unit file; the target need not exist for Lstat.
+	if err := os.Symlink(filepath.Join(unitDir, unit), filepath.Join(wants, unit)); err != nil {
+		t.Skipf("symlink unsupported here (Windows privilege): %v", err)
+	}
+	if !ops.unitEnabled(unit) {
+		t.Fatal("a unit WITH a wants-symlink must report enabled")
+	}
+}