Add per-output palettes and window-scoped theme binding

Each Hyprland/GDK connector can have its own palette and stylesheet
under $XDG_RUNTIME_DIR/bread/{palettes,themes}/. GTK apps bind a
widget-level provider so two windows in one process can follow
different wallpapers. Bump workspace version to 0.7.4 for the tag.

bread-theme/CHANGELOG.md

@@ -1,11 +1,48 @@
 # bread-theme changelog
 
+## 0.7.4
+
+Per-output (per-monitor) theming. Session-global `theme.css` remains the
+fallback / focused-monitor sheet; each Hyprland/GDK connector can now have
+its own palette and stylesheet. BOS still keeps bg/surface/overlay/fg
+fixed — only color1–6 come from the wallpaper.
+
+On disk under `$XDG_RUNTIME_DIR/bread/` (same fallback as `shared_css_path`):
+
+- `palettes/<sanitized-output>.json` — accents only (round-trips through
+  `from_wal_json` / a color1–6 object; never persists pywal's light bg)
+- `themes/<sanitized-output>.css` — `stylesheet()` for that palette
+
+New lib API:
+
+- `themes_dir`, `palettes_dir`, `output_css_path`, `output_palette_path`,
+  `sanitize_output`
+- `load_palette_for`, `write_output_palette`, `write_output_css`,
+  `write_shared_css_from`
+- `palette_from_image` (isolated `wal -i`, does not touch `~/.cache/wal`),
+  `generate_output`, `palette_from_json`
+- `stylesheet_resolved` — inlines `@accent` / `@on-bg` / … to hex so GTK's
+  display-global `@define-color` cannot leak the wrong monitor's accent
+
+GTK (`gtk` feature): `bind_window`, `bind_window_with_app_css`,
+`output_for_widget`, `bind_window_auto`, `bind_window_auto_with_app_css`.
+Widget-scoped providers at `USER - 10` so they beat `apply_shared` but
+lose to user CSS. Existing `apply_shared` / `apply_app_css` /
+`apply_css` / `apply_user_css` are unchanged.
+
+CLI: `bread-theme generate-output <OUTPUT> --image <PATH> | --from-json
+<FILE> [--shared]`. Does not write `theme.css` unless `--shared`.
+
 ## Coordinated bump policy
 
-`bread-theme` is consumed by `breadbar`, `breadbox`, and `breadpad` as a pinned
-git dependency. A breaking change to `Palette`, `css_vars`, or the `gtk` feature
-API requires all three dependents to bump their `Cargo.toml` git tag and cut a
-release together. Note the impact in this file before tagging.
+`bread-theme` is consumed by `breadbar`, `breadbox`, `breadpad`, and the other
+GTK bread apps as a pinned git dependency. A breaking change to `Palette`,
+`css_vars`, or the `gtk` feature API requires dependents to bump their
+`Cargo.toml` git tag and cut a release together. Note the impact in this file
+before tagging.
+
+**0.7.4** adds per-output bind APIs (`bind_window*`, `load_palette_for`,
+`generate_output`). Apps that call those must pin `tag = "v0.7.4"`.
 
 ---