Open PRs from perlowja, suggested review order #281

@mirkobrombin there is a backlog of my PRs across the org, all green on CI.
I rebased the two that conflicted with your recent work and closed one that no
longer applies. Suggested order, smallest first:

Small fixes

• libsingularity #16 build: keep libcups out of the Vala target
• libsingularity #17 fix(animation): bind the drag icon as unowned
• libsingularity #18 fix(style): load user themes above the built-in base
• singularity-write #2 fix(a11y): GtkAccessibleText vfuncs added in GTK 4.22
• singularity-nearby #2 fix: keep an open link when the peer announces itself again
• singularity-leafs #6 fix: keep the window buttons in classic titlebar mode
• singularity-shell #43 fix(plugins): create the extension for an enabled plugin
• singularity-shell #38 fix(overview): keep the app grid clear of the dock
• singularity-greeter #2, #3 session cancel and info/error replies

HiDPI (render at the output scale)

• singularity-shell #40 lock screen
• singularity-greeter #4 greeter, rebased on your shared progress frame
• singularity-loginui #3 reworked: one-factor logo fit in your new layout,
  so a non-square logo no longer stretches or changes shape at the labwc
  handoff

Behaviour

• singularity-shell #39 lock on logind Lock and before sleep
• libsingularity #19 start one lockscreen at a time
• singularity-session #9 per-run logs and crash signal names
• singularity-shell #41 wallpaper attribution, singularity-shell #44 Screensaver and Lock category
• singularity-plugins #7 sensors popover tabs
• singularity-plugins #3 Bing region picker (your Sep 21 points are addressed
  in ab57b5f; see the reply there)

Closed: singularity-loginui #2. loginui_render_splash() has no callers since
the shared progress frame landed.

Two new small PRs will follow (lock keymap failure, About logo aspect). I also
have an optional, off-by-default way for the lock screen to show a screensaver
rendered by another process (about 1.9k lines including a headless test).
Would you want that as a PR, or should it stay downstream?

One question: should the greeter's login card use the same field label as the
lock card (a non-plain PAM prompt like "Enter TPM PIN" shown as the field
label instead of a second line)? I can send that if you want it; if not I will
keep it downstream.