Same pattern as breadbar/breadbox: render the clipboard-history panel,
capture it via bread-screenshots, then exit. One view ("history"), full
known-size canvas capture since the panel isn't its own layer surface.
active_window()/focused_monitor() (used to anchor the panel next to the
real focused window) both resolve to None inside bread-capture's isolated
environment (HYPRLAND_INSTANCE_SIGNATURE is deliberately unset there), so
the panel falls back to its already-existing centered layout — exactly
the deterministic behavior a screenshot needs, with no screenshot-mode-
specific positioning logic required.
Also fixes the same singleton footgun as breadbox: toggle_or_kill()
kills whatever's holding breadclip's single-instance lock, which is
typically the real running instance. A screenshot run now skips it
entirely instead of fighting over (and killing) the operator's real
clipboard panel.
Mirrors tonight's breadbox migration (same shared crate, same duplicated
patterns):
- position.rs's raw socket1 client -> bread_utils::hypr (file removed
entirely, its logic now lives in the shared crate)
- toggle_or_continue's TOCTOU-prone PID-file dance -> bread_utils::singleton
- the layer-shell window setup, Up/Down visible-row navigation, and
click-outside-close gesture -> bread_utils::gtk_popup
- breadclip-core's data_dir(): replaced the buggy
`dirs::data_local_dir().unwrap_or_else(|| PathBuf::from("~/.local/share"))`
fallback (flagged but never fixed in tonight's earlier audit pass —
PathBuf never expands `~`) with bread_utils::xdg::data_dir, which
resolves a real $HOME before ever falling back.
Builds and tests clean across the whole breadclip workspace.
