Add bread-utils and bread-onnx: shared crates for ecosystem-wide duplication

bread-utils extracts genuinely duplicated logic found across breadbox,
breadclip, breadmon, breadcrumbs, bos-settings, and breadhelp:

- hypr: Hyprland socket1 request/response client (breadbox's
  get_active_workspace + breadclip's position.rs hyprctl_json were
  near-identical), socket2 path resolution (breadmon), and a
  version-tolerant `fullscreen` field parser (Hyprland has shipped both
  bool and int representations across versions).
- singleton: correct flock-based single-instance toggle, replacing the
  TOCTOU-prone read-pid/check-proc/kill/write-pid pattern duplicated
  verbatim between breadbox and breadclip (breadclip's own comment says
  "matches breadbox pattern").
- proc: breadcrumbs' timeout-guarded subprocess runner, promoted verbatim
  as the one implementation in the ecosystem that already got this right.
- atomic + xdg: atomic (temp-then-rename) file writes with an optional
  .bak-before-overwrite variant, and XDG path helpers that never fall back
  to a literal "~/..." string (the exact breadclip-core and
  breadpad-shared bug: PathBuf never expands `~`).
- tomlcfg (feature "toml"): the load_doc/save_doc TOML-editing discipline
  bos-settings and breadhelp both implemented byte-for-byte identically in
  the same fix pass that introduced it.
- gtk_popup (feature "gtk"): layer-shell overlay window setup, visible-row
  navigation, and click-outside-close, deduplicated from breadbox and
  breadclip (~150 duplicated lines, per both apps' own "same as breadbox"
  comments).

bread-onnx extracts the embedding pipeline (tokenize -> tensor build ->
mean-pool -> L2-normalize) duplicated near-verbatim between breadarr and
breadsearch, a shared execution-provider session builder with loud EP-
registration logging, and a model download+integrity helper. Defaults AMD
iGPU acceleration to ort::ep::MIGraphX (not ROCm) per this machine's own
breadsearch-gpu-backends lesson: ROCMExecutionProvider silently no-ops to
CPU on distro ROCm onnxruntime builds compiled with --use_migraphx.

Both crates build and pass their own test suites standalone. Consumer
migrations follow in subsequent commits.

bread-utils/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "bread-utils"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+description = "Shared plumbing for the bread ecosystem: Hyprland IPC, single-instance toggling, timeout-guarded subprocess execution, atomic file writes, XDG paths, and a GTK4 layer-shell popup scaffold"
+repository = "https://github.com/Breadway/bread-ecosystem"
+keywords = ["hyprland", "wayland", "xdg", "gtk4"]
+
+[dependencies]
+serde = { workspace = true }
+serde_json = { workspace = true }
+dirs = { workspace = true }
+gtk4 = { version = "0.11", features = ["v4_12"], optional = true }
+gtk4-layer-shell = { version = "0.8", optional = true }
+toml_edit = { version = "0.22", optional = true }
+
+[features]
+# Enable the layer-shell popup scaffold (breadbox, breadclip). Kept optional
+# so headless/daemon consumers (breadmon, breadhelp's CLI half, breadcrumbs)
+# don't have to pull in GTK4 + layer-shell just for `hypr`/`proc`/`xdg`.
+gtk = ["dep:gtk4", "dep:gtk4-layer-shell"]
+# Enable the non-destructive TOML doc load/save discipline (bos-settings,
+# breadhelp). Optional so consumers that don't edit TOML configs (breadbox,
+# breadclip, breadmon, ...) don't pull in toml_edit.
+toml = ["dep:toml_edit"]
+
+[dev-dependencies]
+tempfile = "3"