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/aur/Sia-yay-claude-desktop-constraint.txt

@@ -0,0 +1,31 @@
+Repository                    : aur
+Name                          : claude-desktop
+Version                       : 2.31226.1-1
+Description                   : Official Claude AI desktop app from Anthropic — Chat, Cowork, and Claude Code
+URL                           : https://claude.com/download
+Licenses                      : LicenseRef-Proprietary
+Groups                        : None
+Provides                      : None
+Depends On                    : xdg-utils  xdg-desktop-portal  virtiofsd
+                                util-linux-libs  systemd-libs  socat  pango  nss>=3.100
+                                nspr  mesa  libxtst  libxrandr  libxkbcommon
+                                libxfixes  libxext  libxdamage  libxcomposite
+                                libxcb  libx11  libsecret  libseccomp  libnotify
+                                libdrm  libcups  libcap-ng  hicolor-icon-theme  gtk3
+                                glibc  glib2  gcc-libs  expat  dbus  cairo
+                                at-spi2-core  alsa-lib
+Optional Deps                 : xdg-desktop-portal-kde  xdg-desktop-portal-gtk
+                                libayatana-appindicator  kwallet  gnome-keyring
+Make Deps                     : None
+Check Deps                    : None
+Conflicts With                : claude  claude-desktop-bin
+Replaces                      : None
+AUR URL                       : https://aur.archlinux.org/packages/claude-desktop
+First Submitted               : Sun 05 Jul 2026 01:58:02 AM UTC
+Keywords                      : None
+Last Modified                 : Fri 09 Oct 2026 11:31:19 PM UTC
+Maintainer                    : diazkev314
+Popularity                    : 6.458490
+Votes                         : 21
+Out-of-date                   : No
+