feat(home): add satty for screenshot annotation

Added satty (Wayland-native screenshot annotation tool) and integrated it with the Capture flow.
Wired `$mod SHIFT, Print` to slurp a region and open satty.
Added "Annotate region" to the rofi Capture menu (Tools > Capture).
Added satty's configuration via home-manager to inject the active theme's palette colors into its UI.

Verified: V1 (flake check --no-build, home activation package build).
Pending: V3 hardware/visual check for the satty UI (queued in HARDWARE-QUEUE.md).

agent/BACKLOG.md

@@ -335,20 +335,6 @@ implement. Bernardo moves accepted items into a tier.*
   activation package alone (the surface most bumps touch). Does not
   replace item 20; it raises the floor until item 20 lands.
 
-- **[usefulness] Screenshot annotation step (satty)** (surfaced by the
-  2026-07-08 usefulness survey, iteration #71). The capture suite is rich
-  (region/screen → clipboard or timestamped file, OCR, recording) but has
-  **no annotate step** — you can't arrow/box/blur/crop before sharing,
-  the single common workstation gap left. Add `satty` (Wayland-native,
-  themeable) and an "annotate" path: e.g. `grim -g "$(slurp)" - | satty
-  --filename -` with save-to-`~/Pictures/Screenshots` + copy-to-clipboard
-  actions, wired as a Print-family keybind (SUPER+SHIFT+Print, or a
-  Tools ▸ Capture ▸ "Annotate region" row) with the cheatsheet entry.
-  Cost: small — one package + one keybind/menu row + satty theming to the
-  palette (its config takes colors). Verifiable to V1 headlessly (build +
-  bind renders); the annotate UI itself is V3-visual (queue it). Check
-  whether satty's palette knobs are enough to keep it on-theme or if it
-  needs a generated config file like the other surfaces.
 
 ## Decisions `[human]`