bug#81578: 32.0.50; completion-eager-display + completion-eager-update breaks cycling + automatic tab completion

* Bug One

Repro Steps:

- $ mkdir -p a/b/c
- $ cd a
- $ emacs -Q --eval "(setq completion-eager-display t)" --eval "(setq
completion-eager-update t)"
- Press C-x C-f
- Press TAB twice

Expected behavior:

- The first tab appends "b/" to the minibuffer
- The second tab appends "c/" to the minibuffer
- The minibuffer displays "/path/to/a/b/c/"

Observed behavior:

- The first tab appends "b/" to the minibuffer
- The second tab does nothing
- The minibuffer displays "/path/to/a/b/"
- Further tab presses do nothing

I'm not sure if this is intended behavior, but I couldn't find documentation of
this anywhere if so. It does complicate navigating through singly nested
directories like e.g. java/com/adamniederer/app/ with these settings enabled.

I did test one or the other, but both have to be enabled to exhibit this issue

* Bug Two (probably related)

Repro Steps:

- $ mkdir -p a/b
- $ mkdir -p a/c
- $ cd a
- $ emacs -Q --eval "(setq completion-eager-display t)" --eval "(setq
completion-eager-update t)" --eval "(setq completion-cycle-threshold
t)"
- Press C-x C-f
- Press TAB twice

Expected behavior:

- The first tab appends "./" to the minibuffer
- The second tab cycles, removing "./" and appending "b/"
- The minibuffer displays "/path/to/a/b/"
- Further tab presses continue cycling to c/, ../, etc.

Observed behavior:

- The first tab appends "b/" to the minibuffer
- The second tab does nothing
- The minibuffer displays "/path/to/a/./"
- Further tab presses do nothing

Same notes as above, just with respect to cycling


In GNU Emacs 32.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.52, cairo version 1.18.4) of 2026-08-07 built on pc
Repository revision: a3d43a12a4060430c92145e4c53431ccf20bae58
Repository branch: master
System Description: Arch Linux

Configured using:
 'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --mandir=/usr/share/man --with-gameuser=:games
 --with-modules --without-m17n-flt --without-gconf
 --with-native-compilation=yes --with-native-compilation=aot
 --with-xinput2 --with-pgtk --without-xaw3d --with-sound=no
 --with-tree-sitter 'CFLAGS=-march=native -mtune=native -O2 -pipe
 -fno-plt -fexceptions -Wp,-D_FORTIFY_SOURCE=2 -Wformat
 -Werror=format-security -fstack-clash-protection -fcf-protection'
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
LCMS2 LIBOTF LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY
PDUMPER PGTK PNG RSVG SECCOMP SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS
TREE_SITTER WEBP XIM GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=fcitx5
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  minibuffer-nonselected-mode: t
  minibuffer-regexp-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr comp-run bytecomp byte-compile comp-common rx
emacsbug lisp-mnt message mailcap yank-media puny dired dired-loaddefs
rfc822 mml mml-sec password-cache epa derived epg rfc6068 epg-config
gnus-util text-property-search time-date subr-x mule-util mm-decode
mm-bodies mm-encode mailabbrev gmm-utils mailheader cl-loaddefs cl-lib
sendmail mail-parse rfc2231 rfc2047 rfc2045 ietf-drums mm-util
mail-prsvr mail-utils rmc iso-transl tooltip cconv eldoc paren electric
uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel
term/pgtk-win pgtk-win term/common-win touch-screen pgtk-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow
isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax
font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify
dynamic-setting system-font-setting font-render-setting cairo gtk pgtk
lcms2 multi-tty move-toolbar make-network-process tty-child-frames
native-compile emacs)

Memory information:
((conses 16 55742 9120) (symbols 48 6211 0) (strings 32 15053 1253)
 (string-bytes 1 526502) (vectors 16 9637)
 (vector-slots 8 138526 8530) (floats 8 22 2) (intervals 56 265 0)
 (buffers 1064 10))