fix(schema): add missing background-attribution GSettings keys

[perlowja]

Summary

singularity-shell master reads three keys this schema does not declare:

• show-wallpaper-attribution - read unguarded via
  settings.get_boolean() in desktop_page.vala:317 and
  background.vala:283
• background-attribution-title / background-attribution-author - written
  through SettingsSafety from desktop_page.vala, desktop_icons.vala and
  wallpaper_manager.vala

g_settings_get_boolean() on a key the schema does not declare is a fatal
error, not a catchable one, so opening the Desktop settings page aborts the
process until these keys exist.

Changes since the earlier hold

The hold reason was that these keys only supported the then-unaccepted
wallpaper provider work in singularity-shell#26. #25, #26 and #27 have since
merged, so the readers listed above are on main today - git grep for each
key name finds them.

Rebased onto current master and reduced to the schema alone. The
singularity-shell submodule bump is dropped: master already points at
4945d4d, newer than the c10ad57 this branch carried, so the bump was a
regression as well as an unrelated concern.

Test plan

• glib-compile-schemas accepts the file
• Against the compiled schema, gsettings get dev.sinty.desktop returns
  true, '' and '' for the three new keys
• git grep on singularity-shell main confirms a real reader for each

AI assistance: disclosed

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-09T04:10:11.053943Z	6fe8477	PR opened

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[mirkobrombin]

Holding because its schema and submodule bumps only support the unaccepted wallpaper-provider branch in singularity-shell#26.

[mirkobrombin]

Merged the others, need fix here for the conflicts

[perlowja]

Conflicts fixed and the hold reason has resolved itself. Head is 1a0d96e: one commit on current master, one file, +16 / -0.

The hold. You held this because the keys only supported the then-unaccepted provider work in singularity-shell#26. #25, #26 and #27 have since merged, so those readers are on main today:

• show-wallpaper-attribution - desktop_page.vala:317 and background.vala:283, both unguarded settings.get_boolean()
• background-attribution-title / -author - written from desktop_page.vala, desktop_icons.vala, and watched in wallpaper_manager.vala

g_settings_get_boolean() on a key the schema does not declare is a fatal error, not a catchable one, so as things stand opening the Desktop settings page on master aborts. wallpaper_manager.vala guards its reads with schema.has_key(); the two get_boolean() calls do not. That makes this a fix for already-merged code rather than groundwork for an unmerged branch.

Conflicts. The conflict was the singularity-shell submodule bump, and dropping it is the right resolution rather than re-pointing it: master already points at 4945d4d, which is newer than the c10ad57 this branch carried, so the bump was a regression. It was also a second concern in a schema PR. Gone - the branch is the schema and nothing else.

Verification. glib-compile-schemas accepts the file, and against the compiled schema gsettings get dev.sinty.desktop returns true, '' and '' for the three keys, matching their declared defaults. I also tightened the three <description> strings to one sentence each, to match the surrounding style.

@mirkobrombin no open review object to dismiss here, just the hold comment - flagging that its reason no longer applies. Ready for a look.