fix(show): star marker, aligned gutter and smarter AUR merge

N?? / show marks the upstream candidate with "*" instead of ">" (the
prompt, which read as a command in logs), and every line but the note
gets a two-character gutter: "  " for the installed record, "* " for the
candidate, so keys and colons line up. The plain native fallback (zypper,
unmergeable records) and the not-installed candidate use the same gutter.

pacman records (-Qi with -Si or the AUR helper's -Sia) are now compared
the way they are meant:
- values unwrapped (continuation lines joined, runs of blanks as one):
  yay wraps Depends On / Optional Deps at 80 columns even without a
  terminal unless COLUMNS=0, which the helper now gets for -Qua and -Sia
- Depends On, Provides, Conflicts With, Make/Check Deps and the other
  lists as sets of exact tokens in any order (a constraint is a change)
- Optional Deps by package names ("name: description [installed]" in
  -Qi, bare names from the AUR)
- a differing value is one line like -Qi, Optional Deps one entry per
  line; candidate-only fields sit next to their counterpart (Repository
  after Version, AUR URL after URL, Maintainer after Packager, ...)

Verified on recorded claude-desktop records (paru 2.1.0, yay 13.0.1, the
installed 2.9939.4-1 from the AUR's own .SRCINFO); discovery/pacman.md
section 15.2.

tests/unit/data/pacman/Qi.txt

@@ -332,3 +332,29 @@ Install Date    : Fri Oct  9 08:00:00 2026
 Install Reason  : Explicitly installed
 Install Script  : No
 Validated By    : None
+
+Name            : claude-desktop
+Version         : 2.9939.4-1
+Description     : Official Claude AI desktop app from Anthropic — Chat, Cowork, and Claude Code
+Architecture    : x86_64
+URL             : https://claude.com/download
+Licenses        : LicenseRef-Proprietary
+Groups          : None
+Provides        : None
+Depends On      : alsa-lib  at-spi2-core  cairo  dbus  expat  gcc-libs  glib2  glibc  gtk3  hicolor-icon-theme  libcap-ng  libcups  libdrm  libnotify  libseccomp  libsecret  libx11  libxcb  libxcomposite  libxdamage  libxext  libxfixes  libxkbcommon  libxrandr  libxtst  mesa  nspr  nss  pango  socat  systemd-libs  util-linux-libs  virtiofsd  xdg-desktop-portal  xdg-utils
+Optional Deps   : gnome-keyring: credential storage via Secret Service (GNOME)
+                  kwallet: credential storage (KDE Plasma) [installed]
+                  libayatana-appindicator: system tray icon
+                  xdg-desktop-portal-gtk: portal backend for GTK desktops
+                  xdg-desktop-portal-kde: portal backend for KDE Plasma
+Required By     : None
+Optional For    : None
+Conflicts With  : claude  claude-desktop-bin
+Replaces        : None
+Installed Size  : 117.74 MiB
+Packager        : Unknown Packager
+Build Date      : Sat Oct  3 04:00:00 2026
+Install Date    : Sat Oct 10 13:49:52 2026
+Install Reason  : Explicitly installed
+Install Script  : No
+Validated By    : None