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/e2e/aur.bats

@@ -67,12 +67,12 @@ pacman_only() { [[ $BE == pacman ]] || skip "pacman backend only"; }
 		'su-dummy-aur: Skeptical-updater dummy package AUR (foreign: in no repository)' \
 		'reason: explicitly installed' \
 		'required by: nothing')"
-	assert_line '# lines starting with > come from the upstream candidate: a differing value, or a field the installed record lacks'
-	assert_output --partial "$(printf '%s\n' 'Version         : 1.0-1' '> Version         : 2.0-1')"
-	assert_line 'Install Reason  : Explicitly installed'
-	assert_line '> Repository      : aur'
-	assert_line '> Maintainer      : su-fixture'
-	assert_line '> AUR URL         : https://aur.archlinux.org/packages/su-dummy-aur'
+	assert_line '# lines starting with * come from the upstream candidate: a differing value, or a field the installed record lacks'
+	assert_output --partial "$(printf '%s\n' '  Version         : 1.0-1' '* Version         : 2.0-1' '* Repository      : aur')"
+	assert_line '  Install Reason  : Explicitly installed'
+	assert_output --partial "$(printf '%s\n' '  URL             : https://example.invalid/su-dummy' '* AUR URL         : https://aur.archlinux.org/packages/su-dummy-aur')"
+	assert_output --partial "$(printf '%s\n' '  Packager        : su-fixture <su-fixture@example.invalid>' '* Maintainer      : su-fixture')"
+	assert_output --partial "$(printf '%s\n' '  Validated By    : None' '* Votes           : 7' '* Popularity      : 0.01' '* Out Of Date     : No')"
 	run grep -c 'su-tester HOME=/home/su-tester PWD=/home/su-tester -Sia su-dummy-aur' "$PARU_LOG"
 	assert_output 1
 }